Bunch of fixes to null reference exceptions caused by removing characters mid-round

Barotrauma/Source/Characters/AI/AITarget.cs

@@ -11,7 +11,11 @@ namespace Barotrauma
 
         public static List<AITarget> List = new List<AITarget>();
 
-        public readonly Entity Entity;
+        public Entity Entity
+        {
+            get;
+            private set;
+        }
 
         private float soundRange;
         private float sightRange;
@@ -47,6 +51,7 @@ namespace Barotrauma
         public void Remove()
         {
             List.Remove(this);
+            Entity = null;
         }
 
         public void Draw(SpriteBatch spriteBatch)

Barotrauma/Source/Characters/Animation/Ragdoll.cs

@@ -1513,22 +1513,28 @@ namespace Barotrauma
 
         public void Remove()
         {
-            foreach (Limb l in Limbs)
+            if (Limbs != null)
             {
-                l.Remove();
+                foreach (Limb l in Limbs)
+                {
+                    l.Remove();
+                }
+                Limbs = null;
             }
-            Limbs = null;
 
             foreach (PhysicsBody b in collider)
             {
                 b.Remove();
             }
 
-            foreach (RevoluteJoint joint in LimbJoints)
+            if (LimbJoints != null)
             {
-                GameMain.World.RemoveJoint(joint);
+                foreach (RevoluteJoint joint in LimbJoints)
+                {
+                    GameMain.World.RemoveJoint(joint);
+                }
+                LimbJoints = null;
             }
-            LimbJoints = null;
 
             list.Remove(this);
         }

Barotrauma/Source/Characters/Character.cs

@@ -1959,6 +1959,13 @@ namespace Barotrauma
         
         public override void Remove()
         {
+#if DEBUG
+            if (Removed)
+            {
+                DebugConsole.ThrowError("Attempting to remove an already removed character\n" + Environment.StackTrace);
+            }
+#endif
+
             base.Remove();
 
             if (info != null) info.Remove();

Barotrauma/Source/Networking/EntitySpawner.cs

@@ -109,6 +109,7 @@ namespace Barotrauma
         public void AddToRemoveQueue(Entity entity)
         {
             if (GameMain.Client != null) return;
+            if (removeQueue.Contains(entity) || entity.Removed) return;
 
             removeQueue.Enqueue(entity);
         }
@@ -116,6 +117,7 @@ namespace Barotrauma
         public void AddToRemoveQueue(Item item)
         {
             if (GameMain.Client != null) return;
+            if (removeQueue.Contains(item) || item.Removed) return;
 
             removeQueue.Enqueue(item);
             if (item.ContainedItems == null) return;