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

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);
        }
    }
}