Improve logic when getting unique entities.

src/Bang/World.cs

@@ -941,7 +941,7 @@ public Entity GetUniqueEntity<T>(int index) where T : struct, IComponent
                 }
             }
 
-            Entity? e = context.Entities.LastOrDefault();
+            Entity? e = context.Entities.FirstOrDefault(e => !e.IsDestroyed);
             return e is null || e.IsDestroyed ? null : e;
         }