[MIRROR] Makes tear in the fabric of reality inaccessible until a boh bomb is detonated (#7327)

* Makes tear in the fabric of reality inaccessible until a boh bomb is detonated (#38852)

* a commit message

* reviews addressed?

* Makes tear in the fabric of reality inaccessible until a boh bomb is detonated

code/game/machinery/navbeacon.dm

@@ -37,10 +37,18 @@
 		GLOB.deliverybeacontags += location
 
 /obj/machinery/navbeacon/Destroy()
-	GLOB.navbeacons["[z]"] -= src //Remove from beacon list, if in one.
+	if (GLOB.navbeacons["[z]"])
+		GLOB.navbeacons["[z]"] -= src //Remove from beacon list, if in one.
 	GLOB.deliverybeacons -= src
 	return ..()
 
+/obj/machinery/navbeacon/onTransitZ(old_z, new_z)
+	if (GLOB.navbeacons["[old_z]"])
+		GLOB.navbeacons["[old_z]"] -= src
+	if (GLOB.navbeacons["[new_z]"])
+		GLOB.navbeacons["[new_z]"] += src
+	..()
+
 // set the transponder codes assoc list from codes_txt
 /obj/machinery/navbeacon/proc/set_codes()
 	if(!codes_txt)
@@ -203,4 +211,4 @@ Transponder Codes:<UL>"}
 
 			codes[newkey] = newval
 
-			updateDialog()
+			updateDialog()