Plz Need Help

Error: MissingReferenceException: The object of type ‘GameObject’ has been destroyed but you are still trying to access it.

i have a static GameObject List
when i create object and add this list this is successfully add to list after restrt scene and i am get object from this list so gameobject has destroyed

In GameData, in its Awake or Start method, call

DontDestroyOnLoad(gameObject);