diff --git a/tsconfig.json b/tsconfig.json
index 92cf43fbf82..bcecb172172 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -35,8 +35,6 @@
     "skipLibCheck": true,
     "sourceMap": true,
     "strict": true,
-    "strictPropertyInitialization": false,
-    "useUnknownInCatchVariables": false,
     "stripInternal": true,
     "verbatimModuleSyntax": true,
     "types": [
diff --git a/web_src/js/components/RepoCodeFrequency.vue b/web_src/js/components/RepoCodeFrequency.vue
index 97ce07cc350..146a65995a6 100644
--- a/web_src/js/components/RepoCodeFrequency.vue
+++ b/web_src/js/components/RepoCodeFrequency.vue
@@ -21,6 +21,7 @@ import {
   type DayDataObject,
 } from '../utils/time.ts';
 import {chartJsColors} from '../utils/color.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {sleep} from '../utils.ts';
 import 'chartjs-adapter-dayjs-4/dist/chartjs-adapter-dayjs-4.esm';
 import {onMounted, shallowRef} from 'vue';
@@ -78,7 +79,7 @@ async function fetchGraphData() {
       errorText.value = response.statusText;
     }
   } catch (err) {
-    errorText.value = err.message;
+    errorText.value = errorMessage(err);
   } finally {
     isLoading.value = false;
   }
diff --git a/web_src/js/components/RepoContributors.vue b/web_src/js/components/RepoContributors.vue
index db2f84ecde4..3fd34081e04 100644
--- a/web_src/js/components/RepoContributors.vue
+++ b/web_src/js/components/RepoContributors.vue
@@ -24,6 +24,7 @@ import {
   fillEmptyStartDaysWithZeroes,
 } from '../utils/time.ts';
 import {chartJsColors} from '../utils/color.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {sleep} from '../utils.ts';
 import 'chartjs-adapter-dayjs-4/dist/chartjs-adapter-dayjs-4.esm';
 import {fomanticQuery} from '../modules/fomantic/base.ts';
@@ -166,7 +167,7 @@ export default defineComponent({
           this.errorText = response.statusText;
         }
       } catch (err) {
-        this.errorText = err.message;
+        this.errorText = errorMessage(err);
       } finally {
         this.isLoading = false;
       }
diff --git a/web_src/js/components/RepoRecentCommits.vue b/web_src/js/components/RepoRecentCommits.vue
index 7eb5c7f289b..b58e84e55d6 100644
--- a/web_src/js/components/RepoRecentCommits.vue
+++ b/web_src/js/components/RepoRecentCommits.vue
@@ -20,6 +20,7 @@ import {
   type DayDataObject,
 } from '../utils/time.ts';
 import {chartJsColors} from '../utils/color.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {sleep} from '../utils.ts';
 import 'chartjs-adapter-dayjs-4/dist/chartjs-adapter-dayjs-4.esm';
 import {onMounted, ref, shallowRef} from 'vue';
@@ -74,7 +75,7 @@ async function fetchGraphData() {
       errorText.value = response.statusText;
     }
   } catch (err) {
-    errorText.value = err.message;
+    errorText.value = errorMessage(err);
   } finally {
     isLoading.value = false;
   }
diff --git a/web_src/js/features/admin/config.ts b/web_src/js/features/admin/config.ts
index 5df81412f9b..96c7dcf84bb 100644
--- a/web_src/js/features/admin/config.ts
+++ b/web_src/js/features/admin/config.ts
@@ -2,6 +2,7 @@ import {showTemporaryTooltip} from '../../modules/tippy.ts';
 import {POST} from '../../modules/fetch.ts';
 import {registerGlobalInitFunc} from '../../modules/observer.ts';
 import {queryElems} from '../../utils/dom.ts';
+import {errorMessage} from '../../modules/errors.ts';
 import {submitFormFetchAction} from '../common-fetch-action.ts';
 
 const {appSubUrl} = window.config;
@@ -26,7 +27,7 @@ function initSystemConfigAutoCheckbox(el: HTMLInputElement) {
       const json: Record<string, any> = await resp.json();
       if (json.errorMessage) throw new Error(json.errorMessage);
     } catch (ex) {
-      showTemporaryTooltip(el, ex.toString());
+      showTemporaryTooltip(el, errorMessage(ex));
       el.checked = !el.checked;
     }
   });
diff --git a/web_src/js/features/citation.ts b/web_src/js/features/citation.ts
index 1abd960366e..80eaabcc585 100644
--- a/web_src/js/features/citation.ts
+++ b/web_src/js/features/citation.ts
@@ -1,4 +1,5 @@
 import {getCurrentLocale} from '../utils.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {fomanticQuery} from '../modules/fomantic/base.ts';
 import {localUserSettings} from '../modules/user-settings.ts';
 
@@ -46,7 +47,7 @@ export async function initCitationFileCopyContent() {
     try {
       await initInputCitationValue(citationCopyApa, citationCopyBibtex);
     } catch (e) {
-      console.error(`initCitationFileCopyContent error: ${e}`, e);
+      console.error(`initCitationFileCopyContent error: ${errorMessage(e)}`, e);
       return;
     }
     updateUi();
diff --git a/web_src/js/features/common-fetch-action.ts b/web_src/js/features/common-fetch-action.ts
index 24f4ad2e02f..595bb96c854 100644
--- a/web_src/js/features/common-fetch-action.ts
+++ b/web_src/js/features/common-fetch-action.ts
@@ -1,6 +1,7 @@
 import {GET, request} from '../modules/fetch.ts';
 import {hideToastsAll, showErrorToast} from '../modules/toast.ts';
 import {addDelegatedEventListener, createElementFromHTML} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {confirmModal, createConfirmModal} from './comp/ConfirmModal.ts';
 import {ignoreAreYouSure} from '../vendor/jquery.are-you-sure.ts';
 import {registerGlobalSelectorFunc} from '../modules/observer.ts';
@@ -134,10 +135,10 @@ async function performActionRequest(el: HTMLElement, opt: FetchActionOpts) {
       return;
     }
     await handleFetchActionError(resp);
-  } catch (e) {
-    if (e.name !== 'AbortError') {
-      console.error(`Fetch action request error:`, e);
-      showErrorToast(`Error: ${e.message ?? e}`);
+  } catch (err) {
+    if ((err as Error).name !== 'AbortError') {
+      console.error(`Fetch action request error:`, err);
+      showErrorToast(`Error: ${errorMessage(err)}`);
     }
   } finally {
     toggleLoadingIndicator(el, opt, false);
diff --git a/web_src/js/features/comp/ComboMarkdownEditor.ts b/web_src/js/features/comp/ComboMarkdownEditor.ts
index f16a71a6c57..da7fcd85861 100644
--- a/web_src/js/features/comp/ComboMarkdownEditor.ts
+++ b/web_src/js/features/comp/ComboMarkdownEditor.ts
@@ -71,26 +71,26 @@ export class ComboMarkdownEditor {
 
   options: ComboMarkdownEditorOptions;
 
-  tabEditor: HTMLElement;
-  tabPreviewer: HTMLElement;
+  tabEditor?: HTMLElement;
+  tabPreviewer?: HTMLElement;
 
-  supportEasyMDE: boolean;
+  supportEasyMDE!: boolean;
   easyMDE: any;
   easyMDEToolbarActions: any;
   easyMDEToolbarDefault: any;
 
-  textarea: ComboMarkdownEditorTextarea;
-  textareaMarkdownToolbar: HTMLElement;
+  textarea!: ComboMarkdownEditorTextarea;
+  textareaMarkdownToolbar!: HTMLElement;
   textareaAutosize: any;
 
-  buttonMonospace: HTMLButtonElement;
+  buttonMonospace!: HTMLButtonElement;
 
-  dropzone: HTMLElement | null;
+  dropzone: HTMLElement | null = null;
   attachedDropzoneInst: any;
 
-  previewMode: string;
-  previewUrl: string;
-  previewContext: string;
+  previewMode!: string;
+  previewUrl!: string;
+  previewContext!: string;
 
   constructor(container: ComboMarkdownEditorContainer, options:ComboMarkdownEditorOptions = {}) {
     if (container._giteaComboMarkdownEditor) throw new Error('ComboMarkdownEditor already initialized');
@@ -291,7 +291,7 @@ export class ComboMarkdownEditor {
   }
 
   switchTabToEditor() {
-    this.tabEditor.click();
+    this.tabEditor!.click(); // when this function is called, the tab must exist
   }
 
   prepareEasyMDEToolbarActions() {
diff --git a/web_src/js/features/dropzone.ts b/web_src/js/features/dropzone.ts
index 6ff0cc5a3ae..84076dc93b8 100644
--- a/web_src/js/features/dropzone.ts
+++ b/web_src/js/features/dropzone.ts
@@ -5,6 +5,7 @@ import {showTemporaryTooltip} from '../modules/tippy.ts';
 import {GET, POST} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {createElementFromHTML, createElementFromAttrs} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {isImageFile, isVideoFile} from '../utils.ts';
 import type Dropzone from '@deltablot/dropzone';
 
@@ -149,7 +150,7 @@ export async function initDropzone(dropzoneEl: HTMLElement) {
     } catch (error) {
       // TODO: if listing the existing attachments failed, it should stop from operating the content or attachments,
       //  otherwise the attachments might be lost.
-      showErrorToast(`Failed to load attachments: ${error}`);
+      showErrorToast(`Failed to load attachments: ${errorMessage(error)}`);
       console.error(error);
     }
   });
diff --git a/web_src/js/features/file-view.ts b/web_src/js/features/file-view.ts
index b9a5dd5094f..eed4ba0cd31 100644
--- a/web_src/js/features/file-view.ts
+++ b/web_src/js/features/file-view.ts
@@ -2,6 +2,7 @@ import type {InplaceRenderPlugin} from '../render/plugin.ts';
 import {newInplacePluginPdfViewer} from '../render/plugins/inplace-pdf-viewer.ts';
 import {registerGlobalInitFunc} from '../modules/observer.ts';
 import {createElementFromHTML} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {html} from '../utils/html.ts';
 import {basename} from '../utils.ts';
 
@@ -30,7 +31,7 @@ async function renderRawFileToContainer(container: HTMLElement, rawFileLink: str
       rendered = true;
     }
   } catch (e) {
-    errorMsg = `${e}`;
+    errorMsg = errorMessage(e);
   } finally {
     container.classList.remove('is-loading');
   }
diff --git a/web_src/js/features/imagediff.ts b/web_src/js/features/imagediff.ts
index 1e89aa8b6ec..5351d35ffe0 100644
--- a/web_src/js/features/imagediff.ts
+++ b/web_src/js/features/imagediff.ts
@@ -94,8 +94,8 @@ function createContext(imageAfter: HTMLImageElement, imageBefore: HTMLImageEleme
 }
 
 class ImageDiff {
-  containerEl: HTMLElement;
-  diffContainerWidth: number;
+  containerEl!: HTMLElement;
+  diffContainerWidth!: number;
 
   async init(containerEl: HTMLElement) {
     this.containerEl = containerEl;
diff --git a/web_src/js/features/repo-common.ts b/web_src/js/features/repo-common.ts
index e8fb257c185..65b89cf2612 100644
--- a/web_src/js/features/repo-common.ts
+++ b/web_src/js/features/repo-common.ts
@@ -1,4 +1,5 @@
 import {queryElems} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {POST} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {sleep} from '../utils.ts';
@@ -26,7 +27,7 @@ async function onDownloadArchive(e: Event) {
     window.location.href = el.href; // the archive is ready, start real downloading
   } catch (e) {
     console.error(e);
-    showErrorToast(`Failed to download the archive: ${e}`, {duration: 2500});
+    showErrorToast(`Failed to download the archive: ${errorMessage(e)}`, {duration: 2500});
   } finally {
     targetLoading.classList.remove('is-loading', 'loading-icon-2px');
   }
diff --git a/web_src/js/features/repo-diff.ts b/web_src/js/features/repo-diff.ts
index 500c86fec6a..f866df3526d 100644
--- a/web_src/js/features/repo-diff.ts
+++ b/web_src/js/features/repo-diff.ts
@@ -6,6 +6,7 @@ import {initViewedCheckboxListenerFor, initExpandAndCollapseFilesButton} from '.
 import {initImageDiff} from './imagediff.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {queryElemSiblings, hideElem, showElem, animateOnce, addDelegatedEventListener, createElementFromHTML, queryElems} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {POST, GET} from '../modules/fetch.ts';
 import {createTippy} from '../modules/tippy.ts';
 import {invertFileFolding} from './file-fold.ts';
@@ -85,7 +86,7 @@ function initRepoDiffConversationForm() {
       }
     } catch (error) {
       console.error('Error:', error);
-      showErrorToast(`Submit form failed: ${error}`);
+      showErrorToast(`Submit form failed: ${errorMessage(error)}`);
     } finally {
       form?.classList.remove('is-loading');
     }
diff --git a/web_src/js/features/repo-issue-edit.ts b/web_src/js/features/repo-issue-edit.ts
index 4a112368f46..198951d41f4 100644
--- a/web_src/js/features/repo-issue-edit.ts
+++ b/web_src/js/features/repo-issue-edit.ts
@@ -3,6 +3,7 @@ import {getComboMarkdownEditor, initComboMarkdownEditor, ComboMarkdownEditor} fr
 import {POST} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {hideElem, querySingleVisibleElem, showElem} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {triggerUploadStateChanged} from './comp/EditorUpload.ts';
 import {convertHtmlToMarkdown} from '../markup/html2markdown.ts';
 import {applyAreYouSure, reinitializeAreYouSure} from '../vendor/jquery.are-you-sure.ts';
@@ -73,7 +74,7 @@ async function tryOnEditContent(e: Event) {
       }
       comboMarkdownEditor.dropzoneSubmitReload();
     } catch (error) {
-      showErrorToast(`Failed to save the content: ${error}`);
+      showErrorToast(`Failed to save the content: ${errorMessage(error)}`);
       console.error(error);
     } finally {
       renderContent.classList.remove('is-loading');
diff --git a/web_src/js/features/repo-issue-list.ts b/web_src/js/features/repo-issue-list.ts
index c0cd3c7f22c..046c1beee56 100644
--- a/web_src/js/features/repo-issue-list.ts
+++ b/web_src/js/features/repo-issue-list.ts
@@ -2,6 +2,7 @@ import {updateIssuesMeta} from './repo-common.ts';
 import {toggleElem, queryElems, isElemVisible} from '../utils/dom.ts';
 import {html, htmlRaw} from '../utils/html.ts';
 import {confirmModal} from './comp/ConfirmModal.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {createSortable} from '../modules/sortable.ts';
 import {DELETE, POST} from '../modules/fetch.ts';
@@ -87,7 +88,9 @@ function initRepoIssueListCheckboxes() {
         await updateIssuesMeta(url, action, issueIDs, elementId);
         window.location.reload();
       } catch (err) {
-        showErrorToast(err.responseJSON?.error ?? err.message);
+        // FIXME: this logic (including updateIssuesMeta) is not right, should refactor to our JSONError framework
+        const e = err as {responseJSON?: {error: string}};
+        showErrorToast(e.responseJSON?.error ?? errorMessage(err));
       }
     },
   ));
diff --git a/web_src/js/features/repo-issue-sidebar-combolist.ts b/web_src/js/features/repo-issue-sidebar-combolist.ts
index ab29a18f923..0cea54bbbdb 100644
--- a/web_src/js/features/repo-issue-sidebar-combolist.ts
+++ b/web_src/js/features/repo-issue-sidebar-combolist.ts
@@ -2,6 +2,7 @@ import {fomanticQuery} from '../modules/fomantic/base.ts';
 import {GET, POST} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {addDelegatedEventListener, queryElemChildren, queryElems, toggleElem} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {parseDom} from '../utils.ts';
 
 export function syncIssueMainContentTimelineItems(oldMainContent: Element, newMainContent: Element) {
@@ -42,7 +43,7 @@ export class IssueSidebarComboList {
   elDropdown: HTMLElement;
   elList: HTMLElement | null;
   elComboValue: HTMLInputElement;
-  initialValues: string[];
+  initialValues: string[] = [];
   container: HTMLElement;
 
   elIssueMainContent: HTMLElement;
@@ -129,7 +130,7 @@ export class IssueSidebarComboList {
       await this.reloadPagePartially();
     } catch (e) {
       console.error('Failed to update to backend', e);
-      showErrorToast(`Failed to update to backend: ${e}`);
+      showErrorToast(`Failed to update to backend: ${errorMessage(e)}`);
     } finally {
       this.elIssueSidebar.classList.remove('is-loading');
     }
diff --git a/web_src/js/features/repo-issue.ts b/web_src/js/features/repo-issue.ts
index 03b0c93d85f..7322432fe87 100644
--- a/web_src/js/features/repo-issue.ts
+++ b/web_src/js/features/repo-issue.ts
@@ -1,3 +1,4 @@
+import {errorMessage} from '../modules/errors.ts';
 import {htmlEscape} from '../utils/html.ts';
 import {createTippy} from '../modules/tippy.ts';
 import {
@@ -425,7 +426,7 @@ export function initRepoIssueTitleEdit() {
       window.location.reload();
     } catch (error) {
       console.error(error);
-      showErrorToast(error.message);
+      showErrorToast(errorMessage(error));
     }
   });
 }
diff --git a/web_src/js/features/repo-settings-branches.ts b/web_src/js/features/repo-settings-branches.ts
index 858140adc2f..4e7e74cbc77 100644
--- a/web_src/js/features/repo-settings-branches.ts
+++ b/web_src/js/features/repo-settings-branches.ts
@@ -2,6 +2,7 @@ import {createSortable} from '../modules/sortable.ts';
 import {POST} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {queryElemChildren} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 
 export function initRepoSettingsBranchesDrag() {
   const protectedBranchesList = document.querySelector<HTMLElement>('#protected-branches-list');
@@ -23,8 +24,7 @@ export function initRepoSettingsBranchesDrag() {
             },
           });
         } catch (err) {
-          const errorMessage = String(err);
-          showErrorToast(`Failed to update branch protection rule priority:, error: ${errorMessage}`);
+          showErrorToast(`Failed to update branch protection rule priority: ${errorMessage(err)}`);
         }
       })();
     },
diff --git a/web_src/js/features/user-auth-webauthn.ts b/web_src/js/features/user-auth-webauthn.ts
index 774d41dce0f..f30f4a7f5f4 100644
--- a/web_src/js/features/user-auth-webauthn.ts
+++ b/web_src/js/features/user-auth-webauthn.ts
@@ -1,5 +1,6 @@
 import {encodeURLEncodedBase64, decodeURLEncodedBase64} from '../utils.ts';
 import {hideElem, showElem} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {GET, POST} from '../modules/fetch.ts';
 
 const {appSubUrl} = window.config;
@@ -80,7 +81,7 @@ async function loginPasskey() {
 
     window.location.href = reply?.redirect ?? `${appSubUrl}/`;
   } catch (err) {
-    webAuthnError('general', err.message);
+    webAuthnError('general', errorMessage(err));
   }
 }
 
@@ -104,7 +105,7 @@ async function login2FA() {
     await verifyAssertion(credential);
   } catch (err) {
     if (!options.publicKey.extensions?.appid) {
-      webAuthnError('general', err.message);
+      webAuthnError('general', errorMessage(err));
       return;
     }
     delete options.publicKey.extensions.appid;
@@ -114,7 +115,7 @@ async function login2FA() {
       });
       await verifyAssertion(credential);
     } catch (err) {
-      webAuthnError('general', err.message);
+      webAuthnError('general', errorMessage(err));
     }
   }
 }
@@ -262,6 +263,6 @@ async function webAuthnRegisterRequest() {
     });
     await webauthnRegistered(credential);
   } catch (err) {
-    webAuthnError('unknown', err);
+    webAuthnError('unknown', errorMessage(err));
   }
 }
diff --git a/web_src/js/markup/common.ts b/web_src/js/markup/common.ts
index e826c8fd863..096d8ddf667 100644
--- a/web_src/js/markup/common.ts
+++ b/web_src/js/markup/common.ts
@@ -1,8 +1,10 @@
-export function displayError(el: Element, err: Error): void {
+import {errorMessage} from '../modules/errors.ts';
+
+export function displayError(el: Element, err: unknown): void {
   el.classList.remove('is-loading');
   const errorNode = document.createElement('pre');
   errorNode.setAttribute('class', 'ui message error markup-block-error');
-  errorNode.textContent = err.message || String(err);
+  errorNode.textContent = errorMessage(err);
   el.before(errorNode);
   el.setAttribute('data-render-done', 'true');
 }
diff --git a/web_src/js/markup/render-iframe.ts b/web_src/js/markup/render-iframe.ts
index 2b1b06e5c0b..f05523943a8 100644
--- a/web_src/js/markup/render-iframe.ts
+++ b/web_src/js/markup/render-iframe.ts
@@ -1,4 +1,5 @@
 import {generateElemId} from '../utils/dom.ts';
+import {errorMessage} from '../modules/errors.ts';
 import {isDarkTheme} from '../utils.ts';
 import {GET} from '../modules/fetch.ts';
 
@@ -11,7 +12,7 @@ function safeRenderIframeLink(link: any): string | null {
     }
     return url.href;
   } catch (e) {
-    console.error(`Failed to parse link: ${link}, error: ${e}`);
+    console.error(`Failed to parse link: ${link}, error: ${errorMessage(e)}`);
     return null;
   }
 }
diff --git a/web_src/js/modules/errors.ts b/web_src/js/modules/errors.ts
index ddda0ebe42b..276b498ead7 100644
--- a/web_src/js/modules/errors.ts
+++ b/web_src/js/modules/errors.ts
@@ -2,6 +2,10 @@
 import {html} from '../utils/html.ts';
 import type {Intent} from '../types.ts';
 
+export function errorMessage(err: unknown): string {
+  return (err as Error)?.message || String(err);
+}
+
 export function showGlobalErrorMessage(msg: string, msgType: Intent = 'error') {
   const msgContainer = document.querySelector('.page-content') ?? document.body;
   if (!msgContainer) {
diff --git a/web_src/js/utils/match.ts b/web_src/js/utils/match.ts
index f364481f468..41333d9fa46 100644
--- a/web_src/js/utils/match.ts
+++ b/web_src/js/utils/match.ts
@@ -2,6 +2,7 @@ import emojis from '../../../assets/emoji.json' with {type: 'json'};
 import {GET} from '../modules/fetch.ts';
 import {showErrorToast} from '../modules/toast.ts';
 import {parseIssuePageInfo} from '../utils.ts';
+import {errorMessage} from '../modules/errors.ts';
 import type {Issue, Mention} from '../types.ts';
 
 const maxMatches = 6;
@@ -47,7 +48,7 @@ export function fetchMentions(mentionsUrl: string): Promise<Mention[]> {
       if (!res.ok) throw new Error(res.statusText);
       return await res.json() as Mention[];
     } catch (e) {
-      showErrorToast(`Failed to load mentions: ${e}`);
+      showErrorToast(`Failed to load mentions: ${errorMessage(e)}`);
       return [];
     }
   })();
diff --git a/web_src/js/webcomponents/overflow-menu.ts b/web_src/js/webcomponents/overflow-menu.ts
index 879ce36e6e3..b20d11e2433 100644
--- a/web_src/js/webcomponents/overflow-menu.ts
+++ b/web_src/js/webcomponents/overflow-menu.ts
@@ -3,13 +3,13 @@ import {addDelegatedEventListener, generateElemId, isDocumentFragmentOrElementNo
 import octiconKebabHorizontal from '../../../public/assets/img/svg/octicon-kebab-horizontal.svg';
 
 window.customElements.define('overflow-menu', class extends HTMLElement {
-  popup: HTMLDivElement;
-  overflowItems: Array<HTMLElement>;
-  button: HTMLButtonElement | null;
-  menuItemsEl: HTMLElement;
-  resizeObserver: ResizeObserver;
-  mutationObserver: MutationObserver;
-  lastWidth: number;
+  popup!: HTMLDivElement;
+  overflowItems: Array<HTMLElement> = [];
+  button: HTMLButtonElement | null = null;
+  menuItemsEl!: HTMLElement;
+  resizeObserver!: ResizeObserver;
+  mutationObserver!: MutationObserver;
+  lastWidth!: number;
 
   updateButtonActivationState() {
     if (!this.button || !this.popup) return;
@@ -100,7 +100,7 @@ window.customElements.define('overflow-menu', class extends HTMLElement {
     const itemOverFlowMenuButton = this.querySelector<HTMLButtonElement>('.overflow-menu-button');
 
     // move items in popup back into the menu items for subsequent measurement
-    for (const item of this.overflowItems || []) {
+    for (const item of this.overflowItems) {
       if (!itemFlexSpace || item.getAttribute('data-after-flex-space')) {
         this.menuItemsEl.append(item);
       } else {