qt4 - Main_Interface: show the cone when back from playlist for the --qt-always-video fans like me.

modules/gui/qt4/main_interface.cpp

@@ -696,6 +696,7 @@ void MainInterface::playlist()
             videoWidget->resize( videoWidget->widgetSize );
             videoWidget->updateGeometry();
         }
+        if( bgWidget ) bgWidget->show();
     }
     else
     {