SongEditorPanel : move logic lower down, much metter

fix #576

src/core/include/hydrogen/basics/song.h

@@ -264,9 +264,13 @@ class Song : public H2Core::Object
 		{
 			return __playback_track_enabled;
 		}
-		void	set_playback_track_enabled( bool enabled )
+		bool	set_playback_track_enabled( bool enabled )
 		{
+			if ( __playback_track_filename == NULL ) {
+				return false;
+			}
 			__playback_track_enabled = enabled;
+			return enabled;
 		}
 
 		float	get_playback_track_volume()

src/core/include/hydrogen/hydrogen.h

@@ -238,7 +238,7 @@ class Hydrogen : public H2Core::Object
 	CoreActionController* getCoreActionController() const;
 
 	///playback track
-	void			setPlaybackTrackState(bool);
+	bool			setPlaybackTrackState(bool);
 	bool			getPlaybackTrackState();
 	void			loadPlaybackTrack(QString filename);
 

src/core/src/hydrogen.cpp

@@ -1837,10 +1837,14 @@ void Hydrogen::sequencer_stop()
 	Preferences::get_instance()->setRecordEvents(false);
 }
 
-void Hydrogen::setPlaybackTrackState(bool state)
+bool Hydrogen::setPlaybackTrackState(bool state)
 {
 	Song* pSong = getSong();
-	pSong->set_playback_track_enabled(state);
+	if ( pSong == NULL ) {
+		return false;
+	}
+
+	return pSong->set_playback_track_enabled(state);
 }
 
 void Hydrogen::loadPlaybackTrack(QString filename)

src/gui/src/SongEditor/SongEditorPanel.cpp

@@ -733,22 +733,9 @@ void SongEditorPanel::viewTimeLineBtnPressed( Button* pBtn )
 void SongEditorPanel::mutePlaybackTrackBtnPressed( Button* pBtn )
 {
 	Hydrogen* pEngine = Hydrogen::get_instance();
-	Song* pSong = pEngine->getSong();
-	bool state = true;
 
-	if ( state && pSong == NULL ) {
-		state = false;
-	}
-
-	if ( state && pSong->get_playback_track_filename() == NULL ) {
-		state = false;
-	}
-
-	if ( state ) {
-		state = !pBtn->isPressed();
-	}
-
-	pEngine->setPlaybackTrackState( state );
+	bool state = !pBtn->isPressed();
+	state = pEngine->setPlaybackTrackState( state );
 	m_pMutePlaybackToggleBtn->setPressed( !state );
 }