Prevent multiple Transforms from triggering in the same tick.

This leads to actor duplication.

OpenRA.Game/Actor.cs

@@ -42,6 +42,7 @@ namespace OpenRA
 		public Player Owner { get; internal set; }
 
 		public bool IsInWorld { get; internal set; }
+		public bool WillDispose { get; private set; }
 		public bool Disposed { get; private set; }
 
 		public Activity CurrentActivity { get; private set; }
@@ -284,6 +285,9 @@ namespace OpenRA
 			if (CurrentActivity != null)
 				CurrentActivity.RootActivity.OnActorDisposeOuter(this);
 
+			// Allow traits/activities to prevent a race condition when they depend on disposing the actor (e.g. Transforms)
+			WillDispose = true;
+
 			World.AddFrameEndTask(w =>
 			{
 				if (Disposed)

OpenRA.Mods.Cnc/Traits/ConyardChronoReturn.cs

@@ -204,6 +204,9 @@ namespace OpenRA.Mods.Cnc.Traits
 
 		void ITick.Tick(Actor self)
 		{
+			if (self.WillDispose)
+				return;
+
 			if (triggered)
 				health.InflictDamage(self, chronosphere, new Damage(info.Damage, info.DamageTypes), true);
 

OpenRA.Mods.Common/Activities/Transform.cs

@@ -89,7 +89,7 @@ namespace OpenRA.Mods.Common.Activities
 		{
 			self.World.AddFrameEndTask(w =>
 			{
-				if (self.IsDead)
+				if (self.IsDead || self.WillDispose)
 					return;
 
 				foreach (var nt in self.TraitsImplementing<INotifyTransform>())