Starting from Qt 5.11 QWindow::event is called after QDialog::closeEvent
which would cause a crash if "delete this" was called on closeEvent. The commit
that changed this was e0b5ff4ad5. Added
a check before QWindow::event call utilizing QPointer to prevent the
function call in case object is destroyed by a user in close event handler.
Change-Id: I64a4a0f3271714e55bf7e806177f0d8b39b67fa3
Fixes: QTBUG-84222
Pick-to: 5.15 5.12
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
036c3c19e7