Merge pull request #9304 from atlimit8/Fix_AttackBase_GetMinimumRange

Make AttackBase.GetMinimumRange() return WDist.Zero if there are no available armaments

OpenRA.Game/WDist.cs

@@ -27,6 +27,7 @@ namespace OpenRA
 
 		public WDist(int r) { Length = r; }
 		public static readonly WDist Zero = new WDist(0);
+		public static readonly WDist MaxValue = new WDist(int.MaxValue);
 		public static WDist FromCells(int cells) { return new WDist(1024 * cells); }
 
 		public static WDist operator +(WDist a, WDist b) { return new WDist(a.Length + b.Length); }