User can close parent dialog before closing child dialog

User reported that they found out that it is possible on macOs Qt 5.14.2 to close parent dialog before closing child dialog.

On Windows this is not possible to do.

Example attached and steps to reproduce:

1) Run the application attached.
2) Click on "Press Me" button.
3) A dialog will be opened.
4) Click on "Click Me" button.
5) A MessageBox is shown.
5) Close Dialog, without closing child MessageBox.
6) Click on "OK" in message box.
7) Now again Click on "Press Me" button.