Делаю 2D игру на Юнити.Cобирался сделать мини квесты , создал скрипт quests, добавил его nps ,и вылезла ошибка

Question

NullReferenceException: Object reference not set to an instance of an object Quests.OnTriggerEnter2D (UnityEngine.Collider2D other)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Quests : MonoBehaviour
{
    public int questNumber;
    public int[] items;
    public GameObject[] clouds;
    public GameObject barrier;
    public GameObject key;
public void OnTriggerEnter2D(Collider2D other)
{
    if(other.tag != "Player" && other.gameObject.GetComponent<Pickup>().id == items[questNumber])
    {
        questNumber++;
        Destroy(other.gameObject);
        CheckQuest();
    }
}
public void CheckQuest()
{
    for (int i = 0; i < clouds.Length; i++) 
    {
        if(i == questNumber)
        {
            clouds[i].SetActive(true);
            clouds[i].GetComponent<Animator>().SetTrigger("isTriggered");
            break;
        }
        else
        {
            clouds[i].SetActive(false);
        }
    }
    if(questNumber == 3)
    {
        barrier.SetActive(false);

    }
    if(questNumber == 4) 
    {
        key.SetActive(true);
    }
}

}