Fixed missing mouse event when the Menu control is dismissed

The QQuickPopupWindow doesn't forward the mouse event to the transient window
if the menu is dismissed

Task-number: QTBUG-40391
Change-Id: I2e5fd8b64c63d005445f9fd5e8b36e47b04c1e8b
Reviewed-by: Filippo Cucchetto <filippocucchetto@gmail.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@theqtcompany.com>