Fixed compiler warning

sdrbase/settings/mainsettings.cpp

@@ -23,7 +23,7 @@ MainSettings::~MainSettings()
     }
 }
 
-const QString& MainSettings::getFileLocation() const
+QString MainSettings::getFileLocation() const
 {
     QSettings s;
     return s.fileName();

sdrbase/settings/mainsettings.h

@@ -18,7 +18,7 @@ public:
 	void save() const;
 
 	void resetToDefaults();
-	const QString& getFileLocation() const;
+	QString getFileLocation() const;
 	int getFileFormat() const; //!< see QSettings::Format for the values
 
 	Preset* newPreset(const QString& group, const QString& description);