Fixed a pretty serious issue with containment fields.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@1083 316c924e-a436-60f5-8080-3fe189b3f50e

code/modules/power/singularity/containment_field.dm

@@ -17,9 +17,9 @@
 
 
 	Del()
-		if(FG1)
+		if(FG1 && !FG1.clean_up)
 			FG1.cleanup()
-		if(FG2)
+		if(FG2 && !FG2.clean_up)
 			FG2.cleanup()
 		..()
 

code/modules/power/singularity/field_generator.dm

@@ -19,6 +19,7 @@
 		powerlevel = 0
 		list/obj/machinery/containment_field/fields
 		list/obj/machinery/field_generator/connected_gens
+		clean_up = 0
 
 
 	update_icon()
@@ -310,6 +311,7 @@
 
 
 		cleanup()
+			clean_up = 1
 			for (var/obj/machinery/containment_field/F in fields)
 				if (isnull(F))
 					continue
@@ -321,3 +323,4 @@
 				FG.connected_gens.Remove(src)
 				connected_gens.Remove(FG)
 			connected_gens = list()
+			clean_up = 0