With the refractor in f91e9f8, an abstraction over QtMultiMedia was
implemented. New enums for the PlaybackState were created, to not make
the application depend on QtMultiMedia. However, not all code was
updated to make proper use of these new enums.
This in turn caused the screen turned off while playing a video and the
HUD not showing when the video started buffering. This commit fixes
that.
Closes #51