Restoring geometry of QWidget with a child QWebEngineView may result in assert failure on multi screen setup

If a QWidget is given a parent but it's also given the window flag Qt::Window and a child QWebEngineView, restoring the geometry of the said QWidget may result in:

5.13: ASSERT: "!region.isEmpty() || widgetTextures" in file kernel\qwidgetbackingstore.cpp, line 91
5.14: ASSERT failure in QWidget::mapTo(const QWidget *parent, const QPoint &pos): 
 "parent must be in parent hierarchy", file kernel\qwidget.cpp, line 4064
 

Steps to reproduce:

1. Run the attached project
2. Click the button to create and show the child window QWidget with a webengineview
3. Close the child window to save geometry
4. Move the parent window to a different screen
5. Click the button again to show the child window & restore it's geometry

Additional notes:

• Does not occur without child QWebEngineView
• Does not occur if the QWidget does not have a parent