Fix dead AIs being forced to announce new arrivals (ParadiseSS13#28170)

PR fixes ParadiseSS13#28143

Adds a `stat` check lost in an earlier migration from
`GLOB.alive_mob_list` to `GLOB.ai_list`, to ensure dead AIs aren't added
to the list of announcers.

Author: asciodev

code/modules/mob/new_player/new_player.dm

@@ -401,7 +401,7 @@
 	if(SSticker.current_state == GAME_STATE_PLAYING)
 		var/ailist[] = list()
 		for(var/mob/living/silicon/ai/A in GLOB.ai_list)
-			if(A.announce_arrivals)
+			if(A.stat != DEAD && A.announce_arrivals)
 				ailist += A
 		if(length(ailist))
 			var/mob/living/silicon/ai/announcer = pick(ailist)