[web] Hide pdf-log-entry-content when empty + fixup search "count" color (#21977)

* Hide `PdfLogEntryContent` when there is no content

* Fixup in search "count": `--ol-blue-gray-4` doesn't exist in SCSS

* Update `AiErrorAssistant` with a `shouldRender` export, allowing to hide the element from the caller

* Revert "Update `AiErrorAssistant` with a `shouldRender` export, allowing to hide the element from the caller"

This reverts commit 01812fa2b108b94c99d250c9a39e4f3c41b36781.

* Hide .log-entry-content when empty, using CSS

Co-authored-by: Alf Eaton <alf.eaton@overleaf.com>

---------

Co-authored-by: Alf Eaton <alf.eaton@overleaf.com>
GitOrigin-RevId: c5096b362600058535bd645cf11dad255e941fb9

services/web/frontend/js/features/source-editor/extensions/search.ts

@@ -358,7 +358,7 @@ const searchFormTheme = EditorView.theme({
   },
   '.ol-cm-search-form-position': {
     flexShrink: 0,
-    color: 'var(--ol-blue-gray-4)',
+    color: 'var(--content-secondary)',
   },
   '.ol-cm-search-hidden-inputs': {
     position: 'absolute',