Child window is not closed upon closing the main window in Qt Quick Widgets Example

Linux Ubuntu 22.04 

Qt Creator 12.0.2

Steps to reproduce:

1. Open and run - https://doc.qt.io/qt-6/qtquick-quickwidgets-quickwidget-example.html
2. Click Window > Add tab widget
3. Then click 'Break out to top-level window'
4. Close the main window using 'X' button.
5. Click 'Move back under tab widget'

Expected: The window should be closed when the main window is closed.

Actual: The window is not closed. Clicking 'Move back...' button causes the crash.

Reproducibility:  100%