Problem when starting the world

[Alcaaa]

[Error : Unity Log] NullReferenceException: Object reference not set to an instance of an object
Stack trace:
(wrapper dynamic-method) FejdStartup.DMDFejdStartup::OnWorldStart(FejdStartup)
UnityEngine.Events.InvokableCall.Invoke () (at <50b18efe22344b9eb3b7d77b08ea287f>:0)
UnityEngine.Events.UnityEvent.Invoke () (at <50b18efe22344b9eb3b7d77b08ea287f>:0)
UnityEngine.UI.Button.Press () (at <042da27c9af642978a8a5138113c4eed>:0)
UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at <042da27c9af642978a8a5138113c4eed>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at <042da27c9af642978a8a5138113c4eed>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at <042da27c9af642978a8a5138113c4eed>:0)
UnityEngine.EventSystems.EventSystem:Update()