Prevent attack move crashing if selected actors die.

- Cancel attack move if all actors die.
- Command bar no longer shows available actions from any dead units.

OpenRA.Mods.Common/Widgets/Logic/Ingame/CommandBarLogic.cs

@@ -267,7 +267,7 @@ namespace OpenRA.Mods.Common.Widgets
 				return;
 
 			selectedActors = world.Selection.Actors
-				.Where(a => a.Owner == world.LocalPlayer && a.IsInWorld)
+				.Where(a => a.Owner == world.LocalPlayer && a.IsInWorld && !a.IsDead)
 				.ToArray();
 
 			attackMoveDisabled = !selectedActors.Any(a => a.Info.HasTraitInfo<AttackMoveInfo>() && a.Info.HasTraitInfo<AutoTargetInfo>());