在使用Interface，并且由Monobehaviour继承Interface情况下，判断 interface的实际UnityEngine.Object是否null，出现错误，没有成功的判断出已经Destroy
https://gamedev.stackexchange.com/questions/128971/unity-c-interface-object-never-equals-null
解决方案：
https://discussions.unity.com/t/destroyed-object-not-comparing-to-null/88287
MonoBehaviour == operator is not overriden - it’s Object == operator. But I see that Equals method is overriden
shootTarget == null || shootTarget.Equals(null)
原因：
shootTarget.Equals(null)实际调用的是UnityEngine.Object内复写的Equals，可以检测到UnityObject是否被Destroy
