Pull Request for Issue #45181

Summary of Changes

This PR fixes a bug where filtering articles by Author = None did not return articles created by deleted users. Joomla previously used created_by = 0 for the "None" filter, but in reality, deleted users leave their created_by values intact in the #__content table — they just no longer exist in the #__users table.

This fix updates the logic to:

• Detect when the filter is set to 0 (representing "None")
• Return articles where created_by NOT IN (SELECT id FROM #__users)
• Support multi-select filters, e.g. author_id = [0, 42], to include both deleted users and existing ones

Testing Instructions

1. Create two users in Joomla.
2. Create articles using each user.
3. Delete one of the users via Users > Manage.
4. Go to Content > Articles.
5. Apply the Author filter:
   • Select "None" → should show article by deleted user ✅
   • Select deleted user + another existing user → both articles show ✅
   • Select only existing user → shows only that user’s articles ✅

Actual result BEFORE applying this Pull Request

• Filtering by Author = None shows no articles.
• Deleted users are not handled properly in the query.
• created_by = 0 was used incorrectly.

Expected result AFTER applying this Pull Request

• Articles created by deleted users appear when Author = None is selected.
• Query uses created_by NOT IN (SELECT id FROM #__users) for deleted users.
• Filtering works as expected for mixed author selections (deleted + existing).

Link to documentation

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed