a11y: Accessible interface can't be retrieved after calling QAccessibleEvent::setChild on event created using the constructor taking QAccessibleInterface*

    QWidget widget;
    QWidget childWidget(&widget);

    // QAccessibleEvent constructor called with the QObject*
    QAccessibleEvent event1(&widget, QAccessible::Focus);

    // QAccessibleEvent constructor called with the QAccessibleInterface* for the same QObject*
    QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(&widget);
    QAccessibleEvent event2(iface, QAccessible::Focus);

    // all fine here before calling QAccessibleEvent::setChild
    assert(event1.accessibleInterface() != nullptr);
    assert(event2.accessibleInterface() != nullptr);
    assert(event1.accessibleInterface(), event2.accessibleInterface());

    // set same child for both
    event1.setChild(0);
    event2.setChild(0);

    // this is still OK, case where the ctor taking QObject* was used
    assert(event1.accessibleInterface() != nullptr);
    // these two fail
    assert(event2.accessibleInterface() != nullptr);
    assert(event1.accessibleInterface(), event2.accessibleInterface());