Here another workaround:
- Open Opera
- Press SHIFT+ESC (this opens the Opera Task Manager)
- End process "Extension: Video Handler"
- Repeat step 3 (because it is restarted once)
- Only lasts until you restart Opera
- "Opera Video pop-out" is not available (if you do not know what that is: https://www.youtube.com/watch?v=sEwdu2F_Rdw#t=1m20s