Fixes nuke explosion runtiming if a living mob was in a nullspaced co…

…ntainer (#4659)

# About the pull request

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As per title.

I have no idea what causes this condition to begin with, live inspection
didn't yield any results.

# Explain why it's good for the game
This might sound like an improbable case, and it is, but it actually
happened last week. This caused the nuke explosion to stop and left
everyone confused for the next 45 minutes the round lasted to end
normally.

# Testing Photographs and Procedure
Untested.


# Changelog
:cl:
fix: Fix nuke explosion getting canceled in some very rare cases.
/:cl:

code/game/gamemodes/cm_self_destruct.dm

@@ -259,12 +259,12 @@ var/global/datum/authority/branch/evacuation/EvacuationAuthority //This is initi
 		var/list/alive_mobs = list() //Everyone who will be destroyed on the zlevel(s).
 		var/list/dead_mobs = list() //Everyone who only needs to see the cinematic.
 		for(var/mob/current_mob as anything in GLOB.mob_list) //This only does something cool for the people about to die, but should prove pretty interesting.
-			if(!current_mob || !current_mob.loc)
+			var/turf/current_turf = get_turf(current_mob)
+			if(!current_mob || !current_mob.loc || !current_turf)
 				continue //In case something changes when we sleep().
 			if(current_mob.stat == DEAD)
 				dead_mobs |= current_mob
 				continue
-			var/turf/current_turf = get_turf(current_mob)
 			if(current_turf.z in z_levels)
 				alive_mobs |= current_mob
 				shake_camera(current_mob, 110, 4)
@@ -286,6 +286,8 @@ var/global/datum/authority/branch/evacuation/EvacuationAuthority //This is initi
 		for(var/mob/current_mob in alive_mobs)
 			if(current_mob && current_mob.loc) //Who knows, maybe they escaped, or don't exist anymore.
 				var/turf/current_mob_turf = get_turf(current_mob)
+				if(!current_mob_turf)
+					continue
 				if(current_mob_turf.z in z_levels)
 					if(istype(current_mob.loc, /obj/structure/closet/secure_closet/freezer/fridge))
 						continue