libweston: Add assert for valid confine region in maybe_warp_confined_pointer()

Signed-off-by: Sergio Gómez <sergio.g.delreal@gmail.com>
(cherry picked from commit b6423e59d9116d140e33e925d6dd9bf8324188a7)

libweston/input.c

@@ -4786,6 +4786,7 @@ maybe_warp_confined_pointer(struct weston_pointer_constraint *constraint)
 		pixman_region32_intersect(&confine_region,
 					  &constraint->view->surface->input,
 					  &constraint->region);
+		assert(!pixman_region32_selfcheck(&confine_region));
 		region_to_outline(&confine_region, &borders);
 		pixman_region32_fini(&confine_region);