Mark client as QDELING (#75576)

Clients will now be marked QDELING while in the process of deleting.
Necessary for #75445

code/modules/client/client_procs.dm

@@ -529,6 +529,10 @@ GLOBAL_LIST_INIT(blacklisted_builds, list(
 
 /client/Del()
 	if(!gc_destroyed)
+		gc_destroyed = world.time
+		if (!QDELING(src))
+			stack_trace("Client does not purport to be QDELING, this is going to cause bugs in other places!")
+
 		// Yes this is the same as what's found in qdel(). Yes it does need to be here
 		// Get off my back
 		SEND_SIGNAL(src, COMSIG_PARENT_QDELETING, TRUE)