Reverts ZAS

This reverts commit fd09ea6ce8. and https://github.com/Baystation12/Baystation12/pull/681

code/defines/procs/helpers.dm

@@ -1472,8 +1472,6 @@ 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)
@@ -1483,8 +1481,6 @@ 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)
@@ -1591,4 +1587,4 @@ proc/get_opposite(var/checkdir)
 		var/a = copytext(text,i,i+1)
 		if(a == character)
 			count++
-	return count
+	return count