Notice: Undefined offset: 0 in Drupal\file\FileAccessControlHandler->checkAccess() (line 68 of core/modules/file/src/FileAccessControlHandler.php)

I had the same issue and #2 🐛 Notice: Undefined offset: 0 in Drupal\file\FileAccessControlHandler->checkAccess() (line 68 of core/modules/file/src/FileAccessControlHandler.php) Closed: won't fix cleared the warnings. Curious if this is only something that happens on new installs of the module where the file system is already borked.

This no longer applies

Addressed #7 and raised an MR. Please review.

This same 3 extra check lines should also be added on core/modules/file/src/FileAccessControlHandler.php before line 68 like this:

    if ($operation == 'delete' || $operation == 'update') {
      $account = $this->prepareUser($account);
      if ($entity->get('uid')->isEmpty()) {
        $entity->set('uid', 1);
      }
      $file_uid = $entity->get('uid')->getValue();
      // Only the file owner can update or delete the file entity.
      if ($account->id() == $file_uid[0]['target_id']) {
        return AccessResult::allowed();
      }
      return AccessResult::forbidden('Only the file owner can update or delete the file entity.');
    }

Updated patch for drupal 9.5.9

I'm marking this as won't fix. The latest patch is to core, not to this module. And if there is a problem, I believe that it is in core. Can you reproduce the problem without this module, in just core? If so, then re-open an issue there.