数组显示null引用的UnityEvent错误

这是代码片段。我做错了什么。

using UnityEngine;
using System.Collections;
using UnityEngine.Events;
public class UnityEventSystemDemo : MonoBehaviour {
    UnityEvent[] objUE;
    // Use this for initialization
    void Start () {
        objUE = new UnityEvent[2];
        objUE[0].AddListener(CustomEvent);///Null ref at this point
        objUE[1].AddListener(CustomEvent);
    }
    // Update is called once per frame
    void Update () {
        if (Input.GetMouseButtonDown(0)) {
            Debug.Log("left clicked..");
            //calling Events
            objUE[0].Invoke();
            objUE[1].Invoke();
        }
    }
    void CustomEvent() {
        Debug.Log("customEvent..");
    }
    void CustomEvent1()
    {
        Debug.Log("customEvent1..");
    }
}

NullReferenceException：对象引用未设置为object UnityEventSystemDemo.Update（）（位于Assets/Scripts/UnityEventSystemDemo.cs:23）

objUE = new UnityEvent[2];
objUE[0] = new UnityEvent();
objUE[0].AddListener(CustomEvent);///Null ref at this point
objUE[1] = new UnityEvent();
objUE[1].AddListener(CustomEvent);