Porting pair pinpointers and fixing an edge case runtime.

code/game/objects/items/pinpointer.dm

@@ -26,6 +26,7 @@
 /obj/item/pinpointer/Destroy()
 	STOP_PROCESSING(SSfastprocess, src)
 	GLOB.pinpointer_list -= src
+	target = null
 	return ..()
 
 /obj/item/pinpointer/attack_self(mob/living/user)
@@ -57,7 +58,7 @@
 		return
 	var/turf/here = get_turf(src)
 	var/turf/there = get_turf(target)
-	if(here.z != there.z)
+	if(!here || !there || here.z != there.z)
 		add_overlay("pinon[alert ? "alert" : ""]null")
 		return
 	if(get_dist_euclidian(here,there) <= minimum_range)
@@ -143,3 +144,34 @@
 				target = null
 	if(!target) //target can be set to null from above code, or elsewhere
 		active = FALSE
+
+/obj/item/pinpointer/pair
+	name = "pair pinpointer"
+	desc = "A handheld tracking device that locks onto its other half of the matching pair."
+	var/other_pair
+
+/obj/item/pinpointer/pair/Destroy()
+	other_pair = null
+	. = ..()
+
+/obj/item/pinpointer/pair/scan_for_target()
+	target = other_pair
+
+/obj/item/pinpointer/pair/examine(mob/user)
+	. = ..()
+	if(!active || !target)
+		return
+	var/mob/mob_holder = get(target, /mob)
+	if(istype(mob_holder))
+		to_chat(user, "Its pair is being held by [mob_holder].")
+		return
+
+/obj/item/storage/box/pinpointer_pairs
+	name = "pinpointer pair box"
+
+/obj/item/storage/box/pinpointer_pairs/PopulateContents()
+	var/obj/item/pinpointer/pair/A = new(src)
+	var/obj/item/pinpointer/pair/B = new(src)
+
+	A.other_pair = B
+	B.other_pair = A