同名のオブジェクトがシーンに存在する場合のNullReferenceException:

 同名のオブジェクトがシーンに存在する場合に

複数の個所でFindからインスタンスを得ると競合してしまう

メニュー画面とセーブ画面に使われている同名のボタン（閉じるボタン）に対してクリックリスナーを設定した場合。後から設定されるクリックリスナーが適応される。

＞NullReferenceException: Object reference not set to an instance of an object

YSSave.MyOnClick (System.Int32 index) (at Assets/YSSave.cs:34)

YSSave.<Start>b__4_1 () (at Assets/YSSave.cs:19)

UnityEngine.Events.InvokableCall.Invoke () (at <f1212ad1dec44ce7b7147976b91869c3>:0)

UnityEngine.Events.UnityEvent.Invoke () (at <f1212ad1dec44ce7b7147976b91869c3>:0)

UnityEngine.UI.Button.Press () (at Library/PackageCache/com.unity.ugui@1.0.0/Runtime/UI/Core/Button.cs:70)

UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at Library/PackageCache/com.unity.ugui@1.0.0/Runtime/UI/Core/Button.cs:114)

UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at Library/PackageCache/com.unity.ugui@1.0.0/Runtime/EventSystem/ExecuteEvents.cs:57)

UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at Library/PackageCache/com.unity.ugui@1.0.0/Runtime/EventSystem/ExecuteEvents.cs:272)

UnityEngine.EventSystems.EventSystem:Update() (at Library/PackageCache/com.unity.ugui@1.0.0/Runtime/EventSystem/EventSystem.cs:501)