QML KeyNavigation crashes program

How to reproduce

I attached a minimal example to demonstrate the bug:

1. Start the main.qml in an empty QtCreator QML project. (qmlscene does not reproduce the bug!).
2. Then click the checkbox and press arrow key down -> program crashes with read access violation.

Possible explanation

The Button has "KeyNavigation.up" pointing to the CheckBox. This will implicitly set the

KeyNavigation.down of the CheckBox pointing back to the Button.

Pressing the CheckBox will focus the checkbox and remove the Button from the UI.

Pressing arrow key down will now try to focus the already garbage collected Button.

-> crash