Filter values in the URL that no longer exist empty the list without a visible filter #3947

Initial Checklist

• I understand this is a bug report and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Bug Description

When a filter value in the URL no longer exists, the list is empty but the filter shows nothing selected, so there is no visible reason and nothing to remove.

The views apply the values straight from the URL (Users.vue:198 q_groups/q_roles, Search/List.vue:276 and Favorites.vue:197 q_tags, SharedWithMe.vue:203 q_sharedBy), but ItemFilter.vue:227 only shows values that exist among its loaded items. In admin Users the request also returns 404 without error handling (loadUsersTask).

The App Store already handles this: an unknown tag stays visible as a chip with count 0.

Reproduction Steps

1. Admin settings → Users: filter by a group.
2. Delete that group.
3. Open the filtered URL again (back button or bookmark).

The same with a tag no file has anymore in Search or Favorites, and with a person who no longer shares anything with you in Shared with me.

Expected Outcome

The unknown value stays visible as a selected filter that can be removed, and a failed load shows an error.

Actual Outcome

"No users found", no search results or "Nothing shared, yet", with no filter selected.