fixed various crashes when removing instrument-track with visible instrument-track-window or loading another instrument/preset

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/branches/lmms-mv@712 0778d3d1-df1d-0410-868b-ea421aaaa00d

include/instrument_track.h

@@ -318,6 +318,7 @@ private:
 	QAction * m_midiOutputAction;
 
 	friend class instrumentTrackButton;
+	friend class instrumentView;
 
 } ;
 

include/instrument_view.h

@@ -29,6 +29,8 @@
 #include "instrument.h"
 #include "plugin_view.h"
 
+class instrumentTrackWindow;
+
 
 class instrumentView : public pluginView
 {
@@ -48,6 +50,8 @@ public:
 
 	virtual void setModel( ::model * _model, bool = FALSE );
 
+	instrumentTrackWindow * getInstrumentTrackWindow( void );
+
 } ;