QQuickWidget leads to crash when showing in a QMainWindow, after exiting fullscreen

1. Run the attached demo app on Mac
2. Click "File->Create quick view"
3. A new window will pop up, with a "Dock" button in it. Make this window fullscreen
4. While in full screen, click the "Dock" button. Observe the crash

Expected: When clicking the "Dock" button, the window will show up correctly in the QMainWindow, as its central widget

NOTE: if showNormal() is not used to exit fullscreen, when clicking "Dock" (while in fullscreen), the screen will become grey