LinGui: Fix initialization of audio quality widget limits
When opening the audio edit dialog for a track in the audio list,
the audio quality was set to a bad value because the limits were
not set correctly.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6291 b64f7644-9d1e-0410-96f1-a4d463321fa5