Fix setting MayYieldReservation when there is no reservation

OpenRA.Mods.Common/Activities/Air/AllowYieldingReservation.cs

@@ -0,0 +1,32 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using OpenRA.Activities;
+using OpenRA.Mods.Common.Traits;
+
+namespace OpenRA.Mods.Common.Activities
+{
+	public class AllowYieldingReservation : Activity
+	{
+		readonly Aircraft aircraft;
+
+		public AllowYieldingReservation(Actor self)
+		{
+			aircraft = self.Trait<Aircraft>();
+		}
+
+		public override Activity Tick(Actor self)
+		{
+			aircraft.AllowYieldingReservation();
+			return NextActivity;
+		}
+	}
+}

OpenRA.Mods.Common/Activities/Air/ResupplyAircraft.cs

@@ -42,7 +42,7 @@ namespace OpenRA.Mods.Common.Activities
 				{
 					inner = ActivityUtils.SequenceActivities(
 						aircraft.GetResupplyActivities(host)
-						.Append(new CallFunc(() => aircraft.MayYieldReservation = true))
+						.Append(new AllowYieldingReservation(self))
 						.Append(new WaitFor(() => NextActivity != null || aircraft.ReservedActor == null))
 						.ToArray());
 				}
@@ -52,7 +52,7 @@ namespace OpenRA.Mods.Common.Activities
 					// HACK: Append NextActivity to TakeOff to avoid moving to the Rallypoint (if NextActivity is non-null).
 					inner = ActivityUtils.SequenceActivities(
 						aircraft.GetResupplyActivities(host)
-						.Append(new CallFunc(() => aircraft.MayYieldReservation = true))
+						.Append(new AllowYieldingReservation(self))
 						.Append(new TakeOff(self)).Append(NextActivity).ToArray());
 				}
 			}

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -83,6 +83,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Activities\Air\AllowYieldingReservation.cs" />
     <Compile Include="Activities\Air\FallToEarth.cs" />
     <Compile Include="Activities\Air\Fly.cs" />
     <Compile Include="Activities\Air\FlyAttack.cs" />

OpenRA.Mods.Common/Traits/Air/Aircraft.cs

@@ -111,7 +111,7 @@ namespace OpenRA.Mods.Common.Traits
 		public CPos TopLeft { get { return self.World.Map.CellContaining(CenterPosition); } }
 		public int TurnSpeed { get { return Info.TurnSpeed; } }
 		public Actor ReservedActor { get; private set; }
-		public bool MayYieldReservation;
+		public bool MayYieldReservation { get; private set; }
 
 		bool airborne;
 		bool cruising;
@@ -282,6 +282,14 @@ namespace OpenRA.Mods.Common.Traits
 			}
 		}
 
+		public void AllowYieldingReservation()
+		{
+			if (reservation == null)
+				return;
+
+			MayYieldReservation = true;
+		}
+
 		public void UnReserve()
 		{
 			if (reservation == null)