Previews can't be requested on password-protected links

[JammingBen]

Describe the bug

Requesting a preview for an image on a password protected doesn't work via a GET, only when using signed URLs coming from the server.

Steps to reproduce

1. Upload an image
2. Share it via a password-protected public link
3. Try to get the preview via e.g. https://localhost:9200/remote.php/dav/public-files/{token}/image.jpg?scalingup=0&preview=1&a=1&processor=fit&c=c56553f6ad496a5427a45a702a3c0279, using the encoded password as auth header (e.g. Authorization: Basic cHVibGljOg==).

Expected behavior

The server responds with the preview, just like for non-password link previews.

Actual behavior

The server responds with a 404 error.

Since there is a workaround by using signed URLs, it's not critical IMO. But the web client displays previews in the file list, so it requests the signed URL for every file with every listing. This is not optimal performance-wise as far as I'm aware.