Various Null Access Fixes (#22730)

<img width="1420" height="776" alt="image"
src="https://github.com/user-attachments/assets/d33c4ce2-9c5b-48c3-ac8b-5edfee51c7e0"
/>

Just a few fixes for some various runtime errors and two hard del
triggers on the Sentry logs.

code/modules/events/carp_migration.dm

@@ -96,12 +96,12 @@
 /datum/event/carp_migration/end(var/faked)
 	..()
 
-	for (var/carp_ref in spawned_carp)
-		var/datum/weakref/carp_weakref = carp_ref
+	for (var/datum/weakref/carp_weakref in spawned_carp)
 		var/mob/living/simple_animal/hostile/carp/fish = carp_weakref.resolve()
 		if (fish && prob(50) && is_type_in_typecache(fish.loc, despawn_turfs))
 			spawned_carp -= carp_weakref
 			qdel(carp_weakref)
+	spawned_carp?.Cut()
 
 /datum/event/carp_migration/cozmo/start()
 	..()

code/modules/events/rogue_drones.dm

@@ -34,8 +34,10 @@
 	..()
 
 	var/num_recovered = 0
-	for(var/drone in drones_list)
-		var/mob/living/simple_animal/hostile/icarus_drone/malf/D = drone
+	for(var/mob/living/simple_animal/hostile/icarus_drone/malf/D in drones_list)
+		if (QDELETED(D))
+			continue
+
 		spark(D.loc, 3)
 		D.beam_out()
 		num_recovered++
@@ -45,3 +47,5 @@
 			command_announcement.Announce(SSatlas.current_map.rogue_drone_end_message, "Rogue Drone Alert", new_sound = 'sound/AI/rogue_drone_end_message.ogg', zlevels = affecting_z)
 		else
 			command_announcement.Announce(SSatlas.current_map.rogue_drone_destroyed_message, "Rogue Drone Alert", new_sound = 'sound/AI/rogue_drone_destroyed_message.ogg', zlevels = affecting_z)
+
+	drones_list?.Cut()

code/modules/paperwork/photocopier.dm

@@ -148,7 +148,9 @@
 		return P
 	else if (istype(c_item, /obj/item/paper_bundle))
 		var/obj/item/paper_bundle/B = bundlecopy(target, c_item, TRUE, toner)
-		sleep(15*B.pages.len)
+		if (!B)
+			return FALSE
+		sleep(15 * length(B.pages))
 		return B
 	else
 		to_chat(usr, SPAN_WARNING("\The [c_item] can't be copied by \the [target]."))
@@ -199,7 +201,7 @@
 	c.offset_y = copy.offset_y
 	var/list/temp_overlays = copy.overlays       //Iterates through stamps
 	var/image/img                                //and puts a matching
-	for (var/j = 1, j <= min(temp_overlays.len, copy.ico.len), j++) //gray overlay onto the copy
+	for (var/j = 1, j <= min(length(temp_overlays), length(copy.ico)), j++) //gray overlay onto the copy
 		if (findtext(copy.ico[j], "cap") || findtext(copy.ico[j], "cent"))
 			img = image('icons/obj/bureaucracy.dmi', "paper_stamp-circle")
 		else if (findtext(copy.ico[j], "deny"))
@@ -270,6 +272,8 @@
 
 
 		W = copy_type(target, W, need_toner ? toner : 15, do_print)
+		if (!W)
+			continue
 		W.forceMove(p)
 		p.pages += W