Fix hard dels with rune knives and their creations (#55711)

Rune knives held hard references to the runes they created, which were not cleaned when the rune was eventually deleted. These have been replaced with weakrefs.

code/modules/antagonists/eldritch_cult/eldritch_items.dm

@@ -319,6 +319,10 @@
 	. = ..()
 	linked_action = new(src)
 
+/obj/item/melee/rune_knife/Destroy()
+	. = ..()
+	QDEL_NULL(linked_action)
+
 /obj/item/melee/rune_knife/pickup(mob/user)
 	. = ..()
 	linked_action.Grant(user, src)
@@ -339,10 +343,10 @@
 		to_chat(user,"<span class='notice'>You can't draw runes that close to each other!</span>")
 		return
 
-	for(var/X in current_runes)
-		var/obj/structure/trap/eldritch/eldritch = X
-		if(QDELETED(eldritch) || !eldritch)
-			current_runes -= eldritch
+	for(var/_rune_ref in current_runes)
+		var/datum/weakref/rune_ref = _rune_ref
+		if(!rune_ref.resolve())
+			current_runes -= rune_ref
 
 	if(current_runes.len >= max_rune_amt)
 		to_chat(user,"<span class='notice'>The blade cannot support more runes!</span>")
@@ -369,7 +373,7 @@
 	drawing = FALSE
 	var/obj/structure/trap/eldritch/eldritch = new type(target)
 	eldritch.set_owner(user)
-	current_runes += eldritch
+	current_runes += WEAKREF(eldritch)
 
 /datum/action/innate/rune_shatter
 	name = "Rune break"
@@ -386,10 +390,10 @@
 	return ..()
 
 /datum/action/innate/rune_shatter/Activate()
-	for(var/X in sword.current_runes)
-		var/obj/structure/trap/eldritch/eldritch = X
-		if(!QDELETED(eldritch) && eldritch)
-			qdel(eldritch)
+	for(var/_rune_ref in sword.current_runes)
+		var/datum/weakref/rune_ref = _rune_ref
+		qdel(rune_ref.resolve())
+	sword.current_runes.Cut()
 
 /obj/item/eldritch_potion
 	name = "Brew of Day and Night"

code/modules/antagonists/eldritch_cult/eldritch_structures.dm

@@ -111,14 +111,14 @@
 	desc = "Collection of unknown symbols, they remind you of days long gone..."
 	icon = 'icons/obj/eldritch.dmi'
 	charges = 1
-	///Owner of the trap
-	var/mob/owner
+	/// Weakref containing the owner of the trap
+	var/datum/weakref/owner
 
 /obj/structure/trap/eldritch/Crossed(atom/movable/AM)
 	if(!isliving(AM))
 		return ..()
 	var/mob/living/living_mob = AM
-	if((owner && living_mob == owner) || IS_HERETIC(living_mob) || IS_HERETIC_MONSTER(living_mob))
+	if(living_mob == owner?.resolve() || IS_HERETIC(living_mob) || IS_HERETIC_MONSTER(living_mob))
 		return
 	return ..()
 
@@ -128,8 +128,8 @@
 		qdel(src)
 
 ///Proc that sets the owner
-/obj/structure/trap/eldritch/proc/set_owner(mob/_owner)
-	owner = _owner
+/obj/structure/trap/eldritch/proc/set_owner(mob/owner)
+	src.owner = WEAKREF(owner)
 
 /obj/structure/trap/eldritch/alert
 	name = "alert carving"