How to reproduce

• Edit a content
• Edit a rich-text field and open the "Insert image from the resource explorer" dialog.
• Open a level 2 or 3 folder (which contains files that are not shown here because they are not images) and click on "insert a new resource in the selected folder".
• The folder is reloaded, showing all files in it, including non-images.

Expected behavior

The folder is reloaded, showing only image files.