QuickTestEvent::touchDevice returns invalid QTouchDevice* on second call to quick_test_main (quicktest.h)

I am combining our current test framework with the QtQuickTest framework by calling the generated QUICK_TEST_MAIN wrapper directly instead of running it as an isolated executable to be able to debug the C++ classes which interact with Qml. This works quite well most of the time, but now that we want to support touch devices and test touch with QtQuickTest, it only works for the first call to quick_test_main. All subsequent calls fail because apparently QWindowSystemInterface::unregisterTouchDevice was called for the static test device.