do not crash when loading settings where no file is set

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@746 0778d3d1-df1d-0410-868b-ea421aaaa00d

ChangeLog

@@ -1,5 +1,8 @@
 2008-03-01	Tobias Doerffel	<tobydox/at/users/dot/sourceforge/dot/net>
 
+	* plugins/patman/patman.cpp:
+	do not crash when loading settings where no file is set
+
 	* plugins/triple_oscillator/triple_oscillator.cpp:
 	in saveSettings() fixed wrong integer-to-string-conversion which made
 	LMMS save broken files

plugins/patman/patman.cpp

@@ -170,6 +170,12 @@ void patmanInstrument::deleteNotePluginData( notePlayHandle * _n )
 
 void patmanInstrument::setFile( const QString & _patch_file, bool _rename )
 {
+	if( _patch_file.size() <= 0 )
+	{
+		m_patchFile = QString::null;
+		return;
+	}
+
 	// is current instrument-track-name equal to previous-filename??
 	if( _rename &&
 		( getInstrumentTrack()->name() ==