Fixed exceptions if a character is removed when an AI character is attacking it

Subsurface/Source/Characters/AI/EnemyAIController.cs

@@ -196,7 +196,7 @@ namespace Barotrauma
         
         private void UpdateAttack(float deltaTime)
         {
-            if (selectedAiTarget == null) 
+            if (selectedAiTarget == null || selectedAiTarget.Entity == null || selectedAiTarget.Entity.Removed)
             {
                 state = AiState.None;
                 return;

Subsurface/Source/Characters/AICharacter.cs

@@ -1,11 +1,5 @@
-using Lidgren.Network;
+using Microsoft.Xna.Framework;
-using Microsoft.Xna.Framework;
-using Barotrauma.Networking;
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using FarseerPhysics;
 
 namespace Barotrauma
 {

Subsurface/Source/Characters/Character.cs

@@ -1728,6 +1728,8 @@ namespace Barotrauma
 
         public AttackResult AddDamage(Vector2 worldPosition, DamageType damageType, float amount, float bleedingAmount, float stun, bool playSound, float attackForce = 0.0f)
         {
+            if (Removed) return new AttackResult();
+
             SetStun(stun);
 
             Limb closestLimb = null;

Subsurface/Source/Map/Entity.cs

@@ -16,8 +16,12 @@ namespace Barotrauma
         private ushort id;
 
         protected AITarget aiTarget;
-        //protected float soundRange;
+
-        //protected float sightRange;
+        public bool Removed
+        {
+            get;
+            private set;
+        }
 
         public ushort ID
         {
@@ -125,6 +129,7 @@ namespace Barotrauma
         public virtual void Remove()
         {
             dictionary.Remove(ID);
+            Removed = true;
         }
 
         public static void DumpIds(int count)