Fixes radiation runtime and firebot GC (#2364)

<!-- Write **BELOW** The Headers and **ABOVE** The comments else it may
not be viewable. -->
<!-- You can view Contributing.MD for a detailed description of the pull
request process. -->

## About The Pull Request

Fixes a spurious runtime on checks related to anomalies and radiation,
and makes firebots not hang onto references to targets.

## Why It's Good For The Game

I will fix these test fails one at a time just you watch me

## Changelog

:cl:
tweak: Firebots now extinguish turf fires.
/:cl:

<!-- Both :cl:'s are required for the changelog to work! You can put
your name to the right of the first :cl: if you want to overwrite your
GitHub username as author ingame. -->
<!-- You can use multiple of the same prefix (they're only used for the
icon ingame) and delete the unneeded ones. Despite some of the tags,
changelogs should generally represent how a player might be affected by
the changes rather than a summary of the PR's contents. -->

code/__DEFINES/statpanel.dm

@@ -11,6 +11,4 @@ GLOBAL_LIST_INIT(client_verbs_required, list(
 	/client/verb/forum,
 	/client/verb/github,
 	/client/verb/joindiscord,
-	// Admin help
-	/client/verb/adminhelp,
 ))

code/datums/map_zones.dm

@@ -412,7 +412,7 @@
 			unlink(dir)
 	parent_level.virtual_levels -= src
 	parent_level = null
-	SSidlenpcpool.idle_mobs_by_virtual_level["[id]"] = null
+	LAZYREMOVE(SSidlenpcpool.idle_mobs_by_virtual_level, "[id]")
 	SSmapping.virtual_z_translation -= "[id]"
 	parent_map_zone.remove_virtual_level(src)
 	if(up_linkage)

code/game/objects/effects/anomalies/anomalies_heartbeat.dm

@@ -24,6 +24,9 @@
 
 	COOLDOWN_START(src, pulse_secondary_cooldown, pulse_delay*4)
 	var/turf/spot = locate(rand(src.x-effectrange, src.x+effectrange), rand(src.y-effectrange, src.y+effectrange), src.z)
+	if(!spot)
+		return
+
 	playsound(spot, 'sound/health/slowbeat2.ogg', 100)
 	radiation_pulse(spot, 200, effectrange)
 	for(var/mob/living/carbon/nearby in range(effectrange, spot))

code/modules/mob/living/simple_animal/bot/firebot.dm

@@ -23,8 +23,8 @@
 	window_name = "Mobile Fire Extinguisher v1.0"
 	path_image_color = "#FFA500"
 
-	var/atom/target_fire
-	var/atom/old_target_fire
+	var/datum/weakref/target_fire_ref
+	var/datum/weakref/old_target_fire_ref
 
 	var/obj/item/extinguisher/internal_ext
 
@@ -106,15 +106,15 @@
 
 /mob/living/simple_animal/bot/firebot/bot_reset()
 	..()
-	target_fire = null
-	old_target_fire = null
+	target_fire_ref = null
+	old_target_fire_ref = null
 	ignore_list = list()
 	anchored = FALSE
 	update_appearance()
 
 /mob/living/simple_animal/bot/firebot/proc/soft_reset()
 	path = list()
-	target_fire = null
+	target_fire_ref = null
 	mode = BOT_IDLE
 	last_found = world.time
 	update_appearance()
@@ -149,7 +149,7 @@
 		audible_message("<span class='danger'>[src] buzzes oddly!</span>")
 		playsound(src, "sparks", 75, TRUE, SHORT_RANGE_SOUND_EXTRARANGE)
 		if(user)
-			old_target_fire = user
+			old_target_fire_ref = WEAKREF(user)
 		extinguish_fires = FALSE
 		extinguish_people = TRUE
 
@@ -184,7 +184,7 @@
 
 	else if(isturf(target))
 		var/turf/open/T = target
-		if(T.active_hotspot)
+		if(T.active_hotspot || T.turf_fire)
 			return TRUE
 
 	return FALSE
@@ -194,12 +194,12 @@
 		return
 
 	if(IsStun() || IsParalyzed())
-		old_target_fire = target_fire
-		target_fire = null
+		old_target_fire_ref = target_fire_ref
+		target_fire_ref = null
 		mode = BOT_IDLE
 		return
 
-	if(prob(1) && target_fire == null)
+	if(prob(1) && !target_fire_ref)
 		var/list/messagevoice = list("No fires detected." = 'sound/voice/firebot/nofires.ogg',
 		"Only you can prevent station fires." = 'sound/voice/firebot/onlyyou.ogg',
 		"Temperature nominal." = 'sound/voice/firebot/tempnominal.ogg',
@@ -210,24 +210,39 @@
 
 	// Couldn't reach the target, reset and try again ignoring the old one
 	if(frustration > 8)
-		old_target_fire = target_fire
+		old_target_fire_ref = target_fire_ref
 		soft_reset()
 
+	var/atom/target_fire = target_fire_ref?.resolve()
+
 	// We extinguished our target or it was deleted
 	if(QDELETED(target_fire) || !is_burning(target_fire) || isdead(target_fire))
 		target_fire = null
+		target_fire_ref = null
 		var/scan_range = (stationary_mode ? 1 : DEFAULT_SCAN_RANGE)
+		var/old_target_fire = old_target_fire_ref?.resolve()
 
 		if(extinguish_people)
 			target_fire = scan(/mob/living, old_target_fire, scan_range) // Scan for burning humans first
+			target_fire_ref = WEAKREF(target_fire)
 
-		if(target_fire == null && extinguish_fires)
+		if(!target_fire && extinguish_fires)
 			target_fire = scan(/turf/open, old_target_fire, scan_range) // Scan for burning turfs second
+			target_fire_ref = WEAKREF(target_fire)
 
-		old_target_fire = target_fire
+		old_target_fire_ref = target_fire_ref
+
+	if(!target_fire)
+		if(auto_patrol)
+			if(mode == BOT_IDLE || mode == BOT_START_PATROL)
+				start_patrol()
+
+			if(mode == BOT_PATROL)
+				bot_patrol()
+		return
 
 	// Target reached ENGAGE WATER CANNON
-	if(target_fire && (get_dist(src, target_fire) <= (emagged == 2 ? 1 : 2))) // Make the bot spray water from afar when not emagged
+	if(get_dist(src, target_fire) <= (emagged == 2 ? 1 : 2)) // Make the bot spray water from afar when not emagged
 		if((speech_cooldown + SPEECH_INTERVAL) < world.time)
 			if(ishuman(target_fire))
 				speak("Stop, drop and roll!")
@@ -243,39 +258,32 @@
 		soft_reset()
 
 	// Target ran away
-	else if(target_fire && path.len && (get_dist(target_fire,path[path.len]) > 2))
+	else if(length(path) && (get_dist(target_fire, path[length(path)]) > 2))
 		path = list()
 		mode = BOT_IDLE
 		last_found = world.time
 
-	else if(target_fire && stationary_mode)
+	else if(stationary_mode)
 		soft_reset()
 		return
 
-	if(target_fire && (get_dist(src, target_fire) > 2))
+	if(get_dist(src, target_fire) > 2)
 
 		path = get_path_to(src, get_turf(target_fire), /turf/proc/Distance_cardinal, 0, 30, 1, id=access_card)
 		mode = BOT_MOVING
-		if(!path.len)
+		if(!length(path))
 			soft_reset()
 
-	if(path.len > 0 && target_fire)
+	if(length(path))
 		if(!bot_move(path[path.len]))
-			old_target_fire = target_fire
+			old_target_fire_ref = target_fire_ref
 			soft_reset()
 		return
 
 	// We got a target but it's too far away from us
-	if(path.len > 8 && target_fire)
+	if(length(path) > 8)
 		frustration++
 
-	if(auto_patrol && !target_fire)
-		if(mode == BOT_IDLE || mode == BOT_START_PATROL)
-			start_patrol()
-
-		if(mode == BOT_PATROL)
-			bot_patrol()
-
 
 //Look for burning people or turfs around the bot
 /mob/living/simple_animal/bot/firebot/process_scan(atom/scan_target)