Crash when assigning nullptr to ShellSurfaceItem.shellSurface

Using the QtQuick integration of the QtWayland Compositor, I use shell surfaces to be shown in different ShellSurfaceItems. Specifically, on demand, I assign different shell surfaces to my ShellSurfaceItem.
ShellSurfaceItem can cope with having the shellSurface property being nullptr, initially. But when setting the shellSurface to nullptr later on, after a "proper" shell surface was assigned, the item state is not correctly updated, leading to a crash by accessing the nullptr object.