Fixed unnecessary zero-length array allocations

Changed all currently present zero-length array allocations in the codebase to use `Array.Empty` instead.

OpenRA.Mods.Common/Warheads/FireClusterWarhead.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using OpenRA.GameRules;
@@ -80,8 +81,8 @@ namespace OpenRA.Mods.Common.Warheads
 				CurrentMuzzleFacing = () => (map.CenterOfCell(targetCell) - target.CenterPosition).Yaw,
 
 				DamageModifiers = args.DamageModifiers,
-				InaccuracyModifiers = new int[0],
-				RangeModifiers = new int[0],
+				InaccuracyModifiers = Array.Empty<int>(),
+				RangeModifiers = Array.Empty<int>(),
 
 				Source = target.CenterPosition,
 				CurrentSource = () => target.CenterPosition,