QQuickTapHandler::setPressed() assumes non-null event if not canceled

Seems like this may be the same as QTBUG-118454 except this time it came up while trying to use a TapHandler to open a popup menu which itself has menu items with TapHandlers in them (pure Qt Quick, no Controls, only on X11 not on Wayland):

1   QInputEvent::timestamp                              qevent.h                58
2   QQuickTapHandler::setPressed                        qquicktaphandler.cpp    409 
3   QQuickTapHandler::onGrabChanged                     qquicktaphandler.cpp    478 
4   QQuickDeliveryAgentPrivate::onGrabChanged           qquickdeliveryagent.cpp 1787
5   QtPrivate::FunctorCall<QtPrivate::IndexesList<0, 1  qobjectdefs_impl.h      153 
6   QtPrivate::FunctorCallBase::call_internal<void, Qt, qobjectdefs_impl.h      72  
7   QtPrivate::FunctorCall<QtPrivate::IndexesList<0, 1  qobjectdefs_impl.h      152 
8   QtPrivate::FunctionPointer<void (QQuickDeliveryAge  qobjectdefs_impl.h      200 
9   QtPrivate::QPrivateSlotObject<void (QQuickDelivery  qobject_p.h             284 
10  QtPrivate::QSlotObjectBase::call                    qobjectdefs_impl.h      487 
11  doActivate<false>                                   qobject.cpp             4111
12  QMetaObject::activate                               qobject.cpp             4171
13  QPointingDevice::grabChanged                        moc_qpointingdevice.cpp 296 
14  QPointingDevicePrivate::setExclusiveGrabber         qpointingdevice.cpp     516 
15  QQuickDeliveryAgentPrivate::handleWindowDeactivate  qquickdeliveryagent.cpp 1356
16  QQuickWindow::event                                 qquickwindow.cpp        1624

1. TapHandler has a grab
2. its window is deactivated
3. QQuickDeliveryAgentPrivate::handleWindowDeactivate() calls devPriv->setExclusiveGrabber(nullptr, epd.eventPoint, nullptr);
4. QPointingDevicePrivate::setExclusiveGrabber() emits grabChanged(tapHandler, QPointingDevice::UngrabExclusive, null, eventPoint) : it's UngrabExclusive not CancelGrabExclusive because it's not a take-over: there's no new grabber
5. QQuickTapHandler::onGrabChanged() calls setPressed(false, false, nullptr, eventPoint)

It's correct that TapHandler should no longer be pressed, but it can't access any event properties because there is no event. It should not crash, but it does. If the transition was CancelGrabExclusive we would not have this issue; but the question is did we define correctly what a cancel means? Currently it's decided just on the basis that there is no new grabber: the old grab is not being canceled by being taken over by another grabber. But in a way it's a cancellation of the gesture in progress (like a rug-pull: the window is no longer activated, either because it's no longer shown or because the popup window was activated instead).

Anyway we can add null pointer checks easily enough.