[backport to xwayland-21.1] xwayland: Clear tablet cursor pending frame cb
If the tablet tool is moved out of proximity before the cursor's pending frame callback is received, any further attempts to update the cursor will fail because the frame callback is still pending.
Make sure to clear any cursor pending frame when the tool gets in proximity again, similar to what we do when the pointer re-enters a surface, so that the cursor updates aren't discarded.
Signed-off-by: Olivier Fourdan ofourdan@redhat.com See-also: https://gitlab.gnome.org/GNOME/mutter/-/issues/1969 Reviewed-by: Carlos Garnacho carlosg@gnome.org (cherry picked from commit 35c5664f)