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/Widgets/Logic/Ingame/StanceSelectorLogic.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using System.Linq;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Widgets;
@@ -20,7 +21,7 @@ namespace OpenRA.Mods.Common.Widgets
 		readonly World world;
 
 		int selectionHash;
-		TraitPair<AutoTarget>[] actorStances = { };
+		TraitPair<AutoTarget>[] actorStances = Array.Empty<TraitPair<AutoTarget>>();
 
 		[ObjectCreator.UseCtor]
 		public StanceSelectorLogic(Widget widget, World world)