Adds runtime detection to the atmos ticker. 20 ticks of runtimes, total, will kill atmos.

code/FEA/FEA_system.dm

@@ -104,6 +104,7 @@ datum
 
 			var/current_cycle = 0
 			var/update_delay = 5 //How long between check should it try to process atmos again.
+			var/failed_ticks = 0 //How many ticks have runtimed?
 
 
 /*				process()
@@ -211,9 +212,17 @@ datum
 
 				set background = 1
 				while(1)
-					if(kill_air)
-						return 1
+					if(!kill_air)
 						current_cycle++
+						var/success = tick() //Changed so that a runtime does not crash the ticker.
+						if(!success) //Runtimed.
+							failed_ticks++
+							if(failed_ticks > 20)
+								world << "<font size='4' color='red'>ERROR IN ATMOS TICKER.  Killing air simulation!</font>"
+								kill_air = 1
+					sleep(max(5,update_delay*tick_multiplier))
+
+			proc/tick()
 				if(groups_to_rebuild.len > 0) //If there are groups to rebuild, do so.
 					spawn process_rebuild_select_groups()
 
@@ -228,7 +237,11 @@ datum
 							AG.process_group()
 
 				for(var/turf/simulated/T in active_singletons) //Processing Singletons
-						spawn T.process_cell()
+					spawn
+						if(istype(T))
+							T.process_cell()
+						else
+							active_singletons.Remove(T)
 
 				for(var/turf/simulated/hot_potato in active_super_conductivity) //Process superconduction
 					spawn hot_potato.super_conduct()
@@ -243,7 +256,8 @@ datum
 						spawn
 							if(AG) // Because of runtime errors on syphoning.
 								AG.check_regroup()
-					sleep(max(5,update_delay*tick_multiplier))
+				return 1
+
 
 			proc/process_rebuild_select_groups()
 				//Purpose: This gets called to recalculate and rebuild group geometry