Playlist: fix scrolling events in selector

Close #4092

modules/gui/qt4/components/playlist/selector.cpp

@@ -530,3 +530,9 @@ void PLSelector::getCurrentSelectedItem( int* type, QString *string)
     *type = currentItem()->data( 0, TYPE_ROLE ).toInt();
     *string = currentItem()->data( 0, NAME_ROLE ).toString();
 }
+
+void PLSelector::wheelEvent( QWheelEvent *e )
+{
+    // Accept this event in order to prevent unwanted volume up/down changes
+    e->accept();
+}

modules/gui/qt4/components/playlist/selector.hpp

@@ -123,6 +123,7 @@ protected:
     virtual void dragMoveEvent ( QDragMoveEvent * event );
     virtual bool dropMimeData ( QTreeWidgetItem *, int, const QMimeData *, Qt::DropAction );
     virtual QStringList mimeTypes () const;
+    virtual void wheelEvent(QWheelEvent *e);
 
 private:
     void createItems();