Fix undock anim playing even if docking was cancelled

...before dock anim could run.

The undock animation would play even if the dock anim
hadn't run (meaning the sequence cancelled before the docking
completed, for example due to refinery death).

OpenRA.Mods.Common/Activities/SpriteHarvesterDockSequence.cs

@@ -18,6 +18,7 @@ namespace OpenRA.Mods.Common.Activities
 	{
 		readonly WithSpriteBody wsb;
 		readonly WithDockingAnimationInfo wda;
+		protected bool dockAnimPlayed;
 
 		public SpriteHarvesterDockSequence(Actor self, Actor refinery, WAngle dockAngle, bool isDragRequired, WVec dragOffset, int dragLength)
 			: base(self, refinery, dockAngle, isDragRequired, dragOffset, dragLength)
@@ -32,11 +33,20 @@ namespace OpenRA.Mods.Common.Activities
 				trait.Docked();
 
 			wsb.PlayCustomAnimation(self, wda.DockSequence, () => wsb.PlayCustomAnimationRepeating(self, wda.DockLoopSequence));
+			dockAnimPlayed = true;
 			dockingState = DockingState.Loop;
 		}
 
 		public override void OnStateUndock(Actor self)
 		{
+			// If dock animation hasn't played, we didn't actually dock and have to skip the undock anim and notification
+			if (!dockAnimPlayed)
+			{
+				dockingState = DockingState.Complete;
+				return;
+			}
+
+			dockingState = DockingState.Wait;
 			wsb.PlayCustomAnimationBackwards(self, wda.DockSequence,
 				() =>
 				{
@@ -44,7 +54,6 @@ namespace OpenRA.Mods.Common.Activities
 					foreach (var trait in self.TraitsImplementing<INotifyHarvesterAction>())
 						trait.Undocked();
 				});
-			dockingState = DockingState.Wait;
 		}
 	}
 }