NullReferenceException: Object reference not set to an instance of an object SkillButton.OnPointerEnter (UnityEngine.EventSystems.PointerEventData pointerEventData) (at Assets/Script/UI/SkillButton.cs:11) UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerEnterHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at /Users/builduser/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:22) UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at /Users/builduser/buildslave/unity/build/Extensions/guisystem/UnityEngine.UI/EventSystem/ExecuteEvents.cs:261) UnityEngine.EventSystems.EventSystem:Update()