Lost video file

It seems like my audapolis project lost the connection to a video file.
I changed from 0.2.1 to 0.2.2-pre4 and moved the project and the video file together (they remain next to each other).

**actual behaviour**
When I open the preview I see 'video missing' icon. When I export I get black video.

**expected behaviour**
Error message with some hint on how to fix the problem.

Reproduce the missing-video preview and black export after moving a project and its video file from 0.2.1 to 0.2.2-pre4. Trace how the application resolves the video path and handles missing media; done means the user receives an actionable error message with a hint for fixing the connection.

Written by the indexing model from the issue text.