SampleTrack: fixed non-functional solo and mute buttons
The SampleTrackView did not explicitely have a SampleTrack model
attached and thus trackView::modelChanged() was not called. This way
SampleTrackView's mute and solo buttons were not connected to the
according models of the SampleTrack model. Fix this by calling
setModel() in SampleTrackView::SampleTrackView() (as done in
constructors of other track types too) and overload the
SampleTrackView::modelChanged() method.
Closes #
3043836.
(cherry picked from commit
311bc92bdece8bd969b6278a6d902db3e07e694a)