Fix empty git repo handling logic and fix mobile view (#33101) (#33102)

Backport #33101 and UI fix from main (including #33108)

templates/user/dashboard/navbar.tmpl

@@ -12,7 +12,7 @@
 					{{svg "octicon-triangle-down" 14 "dropdown icon tw-ml-1"}}
 				</span>
 				<div class="context user overflow menu">
-					<div class="ui header">
+					<div class="header">
 						{{ctx.Locale.Tr "home.switch_dashboard_context"}}
 					</div>
 					<div class="scrolling menu items">
@@ -56,7 +56,7 @@
 					</span>
 					{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 					<div class="context user overflow menu">
-						<div class="ui header">
+						<div class="header">
 							{{ctx.Locale.Tr "home.filter_by_team_repositories"}}
 						</div>
 						<div class="scrolling menu items">