Fix some dropdown problems on the issue sidebar (#34308) (#34327)

Backport #34308 by wxiaoguang

Also fix #34300

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/fomantic/build/components/dropdown.js

@@ -4080,7 +4080,7 @@ $.fn.dropdown.settings = {
     search       : 'input.search, .menu > .search > input, .menu input.search',
     sizer        : '> span.sizer',
     text         : '> .text:not(.icon)',
-    unselectable : '.disabled, .filtered',
+    unselectable : '.disabled, .filtered, .tw-hidden', // GITEA-PATCH: tw-hidden hides the item so it is also unselectable
     clearIcon    : '> .remove.icon'
   },