wayland/tablet_v2: Keep also the pad surface in a QPointer
This way we make sure that we don't explode if for some reason the surface is destroyed (e.g. it's closed). This will make it work exactly like the other references to SurfaceInterface.
This way we make sure that we don't explode if for some reason the surface is destroyed (e.g. it's closed). This will make it work exactly like the other references to SurfaceInterface.