How to reproduce
- Upload test video (ask FG)
- Using chrome browser, look at video
=> error message says there is a loading error
- Manually upload a poster frame for the video
=> now everything is ok
The problem is that for some fancy videos the posterframe is empty. This causes Chrome to break.
The fix is to not include the posterframe if not available. We can't fix the root cause, no idea why the poster can't be extracted.