move output damage to workspace destructor

sway/input/seat.c

@@ -381,7 +381,6 @@ void seat_set_focus_warp(struct sway_seat *seat,
 		if (last_ws) {
 			ipc_event_workspace(last_ws, container, "focus");
 			if (last_ws->children->length == 0) {
-				output_damage_whole(last_ws->parent->sway_output);
 				container_destroy(last_ws);
 			}
 		}

sway/tree/container.c

@@ -182,6 +182,9 @@ static struct sway_container *container_workspace_destroy(
 	}
 
 	_container_destroy(workspace);
+
+	output_damage_whole(output->sway_output);
+
 	return parent;
 }