macOS: QMessageBox does not emit the accepted signal when parented

Since the native dialogs are used in Qt 6.5, a parented message box will not emit the accepted signal. Unparented works fine, but it uses a completely different code-path.

Attached is a sample project that shows the problem. Run as is will not emit the signal. When the this parameter on line 13 of widget.cpp is removed, the signal is emitted.

To be clear: this is a regression from previous versions, see the comments below.