compositor: inert wl_surface objects do not exist
compositor: inert wl_surface objects do not exist

There is no valid case, where you would actually destroy a
weston_surface, while leaving the wl_surface protocol object in
existence. Therefore, inert wl_surface objects do not exist, except
because of bugs.

To catch such bugs, check that the resource is really NULL before
actually destroying the weston_surface.

We actually used to have this check, but it was removed by:

	commit 9dadfb53526bc97d62dc01c165e8b6f722f7ea5a
	Author: Kristian Høgsberg <krh@bitplanet.net>
	Date:   Mon Jul 8 13:49:36 2013 -0400

	    compositor: Eliminate marshalling warning for leave events

However, the invariant was put back in:

	commit 0d379744d34e616fea840272deda6b7027f79f55
	Author: Giulio Camuffo <giuliocamuffo@gmail.com>
	Date:   Fri Nov 15 22:06:15 2013 +0100

	    compositor: set weston_surface:resource to NULL when destroyed

So apparently the issue fixed by 9dadfb53 was fixed another way later.

Signed-off-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

Gnurou/weston,Tarnyko/weston-xdg_surface_present,giucam/weston,jonnylamb/weston,Fantu/compositor-spice,xorgy/weston,xorgy/weston,jonnylamb/weston,Fantu/compositor-spice,sir-murray/weston,udoprog/weston,Tarnyko/weston-xdg_surface_present,Gnurou/weston,eyolfson/weston,udoprog/weston,eyolfson/weston,sir-murray/weston,krezovic/weston,mchalupa/weston,kwm81/weston,mchalupa/weston,Fantu/compositor-spice,giucam/weston,krezovic/weston,kwm81/weston