fix previous button, single point of definition

LenaPi/controllers/SettingsHandler.h

@@ -17,6 +17,12 @@ public:
 
     static SettingsHandler* createSettingsHandlerAndFillWithDefaultsIfMissing(QSettings* settings);
 
+    /**
+     * @brief Provides a name filter for QDir that can be used to filter all audio files with valid formats.
+     * @return name filter for QDir
+     */
+    static QStringList getAudioFileNameFilters() {return {"*.mp3", "*.flac"};}
+
     inline void setSettings(QSettings* settings) { mSettings = settings;}
     inline QSettings* getSettings() const { return mSettings; }
     void fillWithDefaultIfMissing();