Merge pull request #690 from Mloc/zas

ZAS bugfixes.

code/ZAS/Processing.dm

@@ -3,7 +3,9 @@ var/explosion_halt = 0
 zone
 	proc/process()
 		if(rebuild)
-			if(!contents) del src
+			if(!contents.len)
+				del src
+				return 0
 			var
 				turf/sample = pick(contents)
 				list/new_contents = FloodFill(sample)

code/defines/procs/helpers.dm

@@ -1429,6 +1429,8 @@ proc/listclearnulls(list/list)
 				air_master.groups_to_rebuild += T1.parent
 			else
 				air_master.tiles_to_update += T1
+			if(T1.zone)
+				T1.zone.space_tiles.len = 0
 
 	if(fromupdate.len)
 		for(var/turf/simulated/T2 in fromupdate)
@@ -1438,6 +1440,8 @@ proc/listclearnulls(list/list)
 				air_master.groups_to_rebuild += T2.parent
 			else
 				air_master.tiles_to_update += T2
+			if(T2.zone)
+				T2.zone.space_tiles.len = 0
 
 	for(var/obj/O in doors)
 		O:update_nearby_tiles(1)
@@ -1544,4 +1548,4 @@ proc/get_opposite(var/checkdir)
 		var/a = copytext(text,i,i+1)
 		if(a == character)
 			count++
-	return count
+	return count