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/game/objects/items/devices/PDA/PDA.dm

@@ -682,7 +682,7 @@ var/global/list/obj/item/device/pda/PDAs = list()
 //EXTRA FUNCTIONS===================================
 
 	if (mode == 2||mode == 21)//To clear message overlays.
-		overlays = null
+		overlays.Cut()
 
 	if ((honkamt > 0) && (prob(60)))//For clown virus.
 		honkamt--
@@ -781,7 +781,7 @@ var/global/list/obj/item/device/pda/PDAs = list()
 			L << "\icon[P] <b>Message from [src.owner] ([ownjob]), </b>\"[t]\" (<a href='byond://?src=\ref[P];choice=Message;skiprefresh=1;target=\ref[src]'>Reply</a>)"
 
 		log_pda("[usr] (PDA: [src.name]) sent \"[t]\" to [P.name]")
-		P.overlays = null
+		P.overlays.Cut()
 		P.overlays += image('icons/obj/pda.dmi', "pda-r")
 	else
 		U << "<span class='notice'>ERROR: Server isn't responding.</span>"

code/game/objects/items/devices/paicard.dm

@@ -110,12 +110,12 @@
 
 /obj/item/device/paicard/proc/removePersonality()
 	src.pai = null
-	src.overlays = null
+	src.overlays.Cut()
 	src.overlays += "pai-off"
 
 /obj/item/device/paicard/proc/setEmotion(var/emotion)
 	if(pai)
-		src.overlays = null
+		src.overlays.Cut()
 		switch(emotion)
 			if(1) src.overlays += "pai-happy"
 			if(2) src.overlays += "pai-cat"

code/game/objects/items/devices/transfer_valve.dm

@@ -115,7 +115,7 @@
 			toggle = 1
 
 /obj/item/device/transfer_valve/update_icon()
-	overlays = null
+	overlays.Cut()
 	underlays = null
 
 	if(!tank_one && !tank_two && !attached_device)