Hello!
Lately we have discovered a bug caused by Unity's IL2CPP which causes Galactic Lander to crash upon trying to select a custom workshop preview for a level in the level editor.
Unfortunately, while we still have not found a solution for this bug, I have come up with a temporary workaround for the issue.
Instead of opening a traditional 'choose file dialog', you must now manually input the full path (plus extension) of the custom preview image.
This isn't desirable, and this will be removed once a permanent fix is found, but until then this workaround will sadly have to stay around.
Thank you for your understanding and patience, and have fun!
- ZeroByter