QWidgetAction cannot render complex widget correctly

Reproducer attached. It shows a QMainWindow whose context menu event is overridden. By right click in the window a QMenu with a sub menu pops up. That sub menu is going to to show a QWidgetAction that should be a QLabel.

The problem is that the QLabel is put into a layout which is set as the layout as a "root" QWidget. And that "root widget" is set as the default widget of QWidgetAction, i.e. "setDefaultWidget(pWidget);" inside PriorityActionWidget constructor. Then the result looks like:

So actually QWidgetAction is not rendering its widget at all.

The workaround I found so far is to set the label as the default widget, i.e. "setDefaultWidget(label);". Then QLabel is visible. But the result is not as pretty as expected. That is the reason I suspect that QWidgetAction may have problem dealing with "complex" widgets (QLabel->QLayout->QWidget) since a simple QLabel works.

It is said that the latest "dev" branch can give expected result. I've tried the 6.10.0 snapshot that I download from online installer - the problem is still there. So some commits between that 6.10.0 snapshot being packed into online installer and the latest branch must have solved the problem. So please backport.