为什么我得到NullReferenceException时，试图在Unity c#中创建一个健康包

好了，伙计们，姑娘们，我又遇到了一些代码的问题。基本上，一旦我开始，它试图创建一个生命值包，它抛出一个错误:

NullReferenceException:对象引用未设置为对象的实例HealthSpawnerScript。更新()(在Assets/Scripts/HealthSpawnerScript.cs:31)

下面是我正在运行的代码。游戏对象PlayerController包含一个名为PlayerHealth()的方法，用于返回玩家健康值。在清醒时，我设置playerController找到脚本和方法后，我。然后在更新中，我试图调用该方法并将其分配给变量，以便稍后在脚本中使用。我知道这应该很简单，但我有一个大脑屁，伙计们。

public PlayerController playerController;
private int healthHolder;
void OnAwake()
{
    playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();
}
// Use this for initialization
void Start () 
{
    //set healthExist to false to indicate no health packs exist on game start
    healthExist = false;
    //playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();
}
// Update is called once per frame
void Update () 
{
    healthHolder = playerController.PlayerHealth();

playerController = GameObject.Find ("PlayerHealth").GetComponent<PlayerController> ();

void Awake()
{
    GameObject obj = GameObject.Find("PlayerHealth");
    if (obj == null)
    {
        Debug.Log("Failed to find PlayerHealth GameObject");
        return;
    }
    playerController = obj.GetComponent<PlayerController>();
    if (playerController == null)
    {
        Debug.Log("No PlayerController script is attached to obj");
    }
}