Mac: QWidgets embedded in QGraphicsProxyWidget are sent closeEvents when app is closed

This is a major regression in Qt 5.

Our application embeds multiple QWidgets into QGraphicsProxyWidgets within a graphics scene.

When the application quits (press CMQ-Q or close window) and the save-confirmation dialog appears, the QWidgets in the scene all vanish! This happens regardless of the user's choice in the confirmation dialog (e.g. the click cancel).

As of Qt 5, the embedded widgets are sent closeEvents and as the default behavior is to accept the event, the widgets are closed.

This does not happen in Qt 4. Only top-level widgets are sent the closeEvent as you would expect.