Merge pull request #12091 from Heroman3003/aifix2

Fixes AI subsystem locking up on trying to process null entries

code/controllers/subsystems/ai.dm

@@ -32,8 +32,11 @@ SUBSYSTEM_DEF(ai)
 	while(currentrun.len)
 		var/datum/ai_holder/A = currentrun[currentrun.len]
 		--currentrun.len
+		if(!A || QDELETED(A) || A.busy) // Doesn't exist or won't exist soon or not doing it this tick
+			continue
+
 		var/mob/living/L = A.holder	//VOREStation Edit Start
-		if(!A || QDELETED(A) || !L?.loc || A.busy) // Doesn't exist or won't exist soon or not doing it this tick
+		if(!L?.loc)
 			continue
 
 		if(process_z[get_z(L)] || !L.low_priority) //VOREStation Edit End

code/modules/ai/ai_holder.dm

@@ -291,6 +291,9 @@
 
 // 'Tactical' processes such as moving a step, meleeing an enemy, firing a projectile, and other fairly cheap actions that need to happen quickly.
 /datum/ai_holder/proc/handle_tactics()
+	if(!istype(holder) || QDELETED(holder))
+		qdel(src)
+		return
 	if(holder.key && !autopilot)
 		return
 	handle_special_tactic()
@@ -298,6 +301,9 @@
 
 // 'Strategical' processes that are more expensive on the CPU and so don't get run as often as the above proc, such as A* pathfinding or robust targeting.
 /datum/ai_holder/proc/handle_strategicals()
+	if(!istype(holder) || QDELETED(holder))
+		qdel(src)
+		return
 	if(holder.key && !autopilot)
 		return
 	handle_special_strategical()