Error 500 when opening the gallery #2920

Describe the bug
When I try to insert an image on a page I get an error 500 from the server

Steps To Reproduce
Steps to reproduce the behavior:

1. Edit a page
2. Click on 'Insert an image'
3. See error GET https://example.com/images/gallery?page=1&uploaded_to=142 500 in the browser console

Expected behavior
Gallery shows images that were uploaded

Screenshots
If applicable, add screenshots to help explain your problem.

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): BookStack v21.08.2
• PHP Version: 7.4.23
• Hosting Method (Nginx/Apache/Docker): Docker Image from here: https://hub.docker.com/r/linuxserver/bookstack

Additional context
I tried to debug the error but can't find anything related in the error logs at storage/logs/laravel.log and even setting the APP_DEBUG=true in the .env file didn't reveal any information on the error (I think the setting didn't change anything at all).