Designer issues warning on exit when the editor for QTableWidget was opened in meantime

To reproduce:
1) Create a new widget form
2) Insert a QTableWidget
3) Double click on the inserted table
4) Close the editor and close the designer without saving the form. I see couple of warnings on console: ~QX11PixmapData(): QPixmap objects must be destroyed before the QApplication object, otherwise the native pixmap object will be leaked.