fix: removing an object from hierarchy setting all children's parents null

Engine.Core/GameManager.cs

@@ -68,6 +68,12 @@ public class GameManager : BaseEntity, IGameManager
     }
 
     public void Remove(IHierarchyObject hierarchyObject)
+    {
+        hierarchyObject.SetParent(null);
+        RemoveIncursive(hierarchyObject);
+    }
+
+    private void RemoveIncursive(IHierarchyObject hierarchyObject)
     {
         if (!_hierarchyObjects.Contains(hierarchyObject))
             throw new Exception($"{nameof(IHierarchyObject)} named {hierarchyObject.Name} is not registered to the {nameof(GameManager)}.");
@@ -79,7 +85,6 @@ public class GameManager : BaseEntity, IGameManager
             Remove(hierarchyObject.Children[i]);
 
         _hierarchyObjects.Remove(hierarchyObject);
-        hierarchyObject.SetParent(null);
 
         if (!hierarchyObject.ExitHierarchy())
             throw new Exception($"{hierarchyObject.Name} can't exit the hierarchy");