qt4: try to read playlist headers state in same group we write them

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

@@ -312,6 +312,7 @@ void StandardPLPanel::createTreeView()
     /* setModel after setSortingEnabled(true), or the model will sort immediately! */
     treeView->setModel( model );
 
+    getSettings()->beginGroup("Playlist");
     if( getSettings()->contains( "headerStateV2" ) )
     {
         treeView->header()->restoreState(
@@ -326,6 +327,7 @@ void StandardPLPanel::createTreeView()
             else if( m == COLUMN_DURATION ) treeView->header()->resizeSection( c, 80 );
         }
     }
+    getSettings()->endGroup();
 
     /* Connections for the TreeView */
     CONNECT( treeView, activated( const QModelIndex& ),