Fixes some rando failures off the ignore list of projectiles (#82855)

code/modules/projectiles/projectile.dm

@@ -457,7 +457,7 @@
 	if(!trajectory)
 		qdel(src)
 		return FALSE
-	if(impacted[A]) // NEVER doublehit
+	if(impacted[A.weak_reference]) // NEVER doublehit
 		return FALSE
 	var/datum/point/point_cache = trajectory.copy_to()
 	var/turf/T = get_turf(A)
@@ -510,7 +510,7 @@
 	if(QDELETED(src) || !T || !target)
 		return
 	// 2.
-	impacted[target] = TRUE //hash lookup > in for performance in hit-checking
+	impacted[WEAKREF(target)] = TRUE //hash lookup > in for performance in hit-checking
 	// 3.
 	var/mode = prehit_pierce(target)
 	if(mode == PROJECTILE_DELETE_WITHOUT_HITTING)
@@ -587,7 +587,7 @@
 //Returns true if the target atom is on our current turf and above the right layer
 //If direct target is true it's the originally clicked target.
 /obj/projectile/proc/can_hit_target(atom/target, direct_target = FALSE, ignore_loc = FALSE, cross_failed = FALSE)
-	if(QDELETED(target) || impacted[target])
+	if(QDELETED(target) || impacted[target.weak_reference])
 		return FALSE
 	if(!ignore_loc && (loc != target.loc) && !(can_hit_turfs && direct_target && loc == target))
 		return FALSE
@@ -675,7 +675,7 @@
  * Used to not even attempt to Bump() or fail to Cross() anything we already hit.
  */
 /obj/projectile/CanPassThrough(atom/blocker, movement_dir, blocker_opinion)
-	return impacted[blocker] ? TRUE : ..()
+	return ..() || impacted[blocker.weak_reference]
 
 /**
  * Projectile moved:
@@ -1188,8 +1188,7 @@
 	bullet.starting = startloc
 	var/list/ignore = list()
 	for (var/atom/thing as anything in ignore_targets)
-		ignore[thing] = TRUE
-	bullet.impacted += ignore
+		bullet.impacted[WEAKREF(thing)] = TRUE
 	bullet.firer = firer || src
 	bullet.fired_from = src
 	bullet.yo = target.y - startloc.y