Fix property strict typing
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3529336. -->
Reported by: [claudiu.cristea](https://www.drupal.org/user/56348)
Related to !6
>>>
<p>Getting </p>
<blockquote><p>
TypeError: Cannot assign null to property Drupal\file_visibility_track_usage\Plugin\FileVisibility\TrackUsage::$trackConfig</p></blockquote>
issue