MonoBehaviour 腳本無法從 ScriptableObject 腳本調用函數

MonoBehaviour 腳本：

    public class MakeObjectMoveOnPath : MonoBehaviour
{

    public WaveConfig settings;


    // Start is called before the first frame update
    void Start()
    {

        settings.OnUse();

    }

    // Update is called once per frame
    void Update()
    {


    }
}

ScriptableObject 腳本：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[CreateAssetMenu(menuName = "Enemy wave config")]
//a scirptable object is an object which is set from scirpt and used from unity


public class WaveConfig : ScriptableObject
{
  

    public void OnUse()
    {
        Debug.Log("Test");
    }



    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}

我想做的是測試我是否可以在調試控制台中從 MonoBehaviour 腳本調用 ScriptableObject 腳本中的方法。確保腳本在統一 2D 中工作但它給了我一個名為

NullReferenceException：未將對象引用設置為對象的實例