Dangling pointer in touch events processing

Method

QQuickWindowPrivate::deliverPressOrReleaseEvent

Build array of QQuickItems under touch points

 QVector<QQuickItem *> targetItems

then iterate through this array and send events, but during this job some QQuickItem could be destroyed, which leads us to corrupted pointers in the array.

Problem detected when we bind 'Item.layer.enabled' to focus state, like in attached file
main.qml

Try to launch 'main.qml' on device with multitouch  support, then press one red rectangle with one finger and second with another finger while first rectangle still pressed - application crash immediately.

In my opinion best solution is to change  QVector<QQuickItem *> to QVector<QPoint<QQuickItem> > and check array items for 'null', but we also provide solution for exactly described case  by using QQuickItemLayer::m_effect->deleteLater instead of delete it instantly

There a change for it: 
https://codereview.qt-project.org/c/qt/qtdeclarative/+/321499