do not call method on deleted trackView but fetch pointer to track before deleting trackView (fixes crash when removing a track)

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@1779 0778d3d1-df1d-0410-868b-ea421aaaa00d

src/gui/track_container_view.cpp

@@ -239,11 +239,12 @@ void trackContainerView::createTrackView( track * _t )
 
 void trackContainerView::deleteTrackView( trackView * _tv )
 {
+	track * t = _tv->getTrack();
 	removeTrackView( _tv );
 	delete _tv;
 
 	engine::getMixer()->lock();
-	delete _tv->getTrack();
+	delete t;
 	engine::getMixer()->unlock();
 }