Too remove potential excessive garbage collection per tick. We will be reusing lists for overlays instead of deleting and creating them.

the .Cut() proc on a list will empty a list by default. This also will set the len to 0.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@5465 316c924e-a436-60f5-8080-3fe189b3f50e

code/modules/power/generator.dm

@@ -43,9 +43,9 @@
 /obj/machinery/power/generator/proc/updateicon()
 
 	if(stat & (NOPOWER|BROKEN))
-		overlays = null
+		overlays.Cut()
 	else
-		overlays = null
+		overlays.Cut()
 
 		if(lastgenlev != 0)
 			overlays += image('icons/obj/power.dmi', "teg-op[lastgenlev]")