Qt4: pictureflow, check that we use valid index

modules/gui/qt4/util/pictureflow.cpp

@@ -448,6 +448,8 @@ void PictureFlowSoftwareRenderer::paint()
 
     QModelIndex index = state->model->index( state->centerIndex, 0, state->model->currentIndex().parent() );
 
+    if( index.isValid() )
+    {
           QString title = PLModel::getMeta( index, COLUMN_TITLE );
           QString artist = PLModel::getMeta( index, COLUMN_ARTIST );
           QFont font( index.data( Qt::FontRole ).value<QFont>() );
@@ -463,6 +465,7 @@ void PictureFlowSoftwareRenderer::paint()
 
           textstart += artiststart;
           painter.drawText( textstart, artist);
+    }
 }
 
 void PictureFlowSoftwareRenderer::init()