fix attack crashing game

OpenRa.Game/Traits/AttackTurreted.cs

@@ -26,10 +26,13 @@ namespace OpenRa.Game.Traits
 
 		protected override void QueueAttack( Actor self, Order order )
 		{
-			var b = self.traits.Get<Building>();
-			if (b != null && b.InsuffientPower())
-				return;
-
+			if (self.traits.Contains<Building>()) 
+			{
+				var b = self.traits.Get<Building>();
+				if (b != null && b.InsuffientPower())
+					return;
+			}
+			
 			const int RangeTolerance = 1;	/* how far inside our maximum range we should try to sit */
 			/* todo: choose the appropriate weapon, when only one works against this target */
 			var weapon = order.Subject.Info.Primary ?? order.Subject.Info.Secondary;
@@ -39,6 +42,7 @@ namespace OpenRa.Game.Traits
 					Math.Max( 0, (int)Rules.WeaponInfo[ weapon ].Range - RangeTolerance ) ) );
 
 			target = order.TargetActor;
+			
 		}
 
 		bool buildComplete = false;