Unity hatam var yardımcı olacak

Unity
1

böyle bir kodum var
using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

public class pipe_spawner : MonoBehaviour
{
public birdflap bird;
public GameObject borular;
public float height;

private void Start()
{
    StartCoroutine(SpawnObject());
}

public IEnumerator SpawnObject()
{
    while (!bird.isdead)
    {
        yield return new WaitForSeconds(1f);
        Instantiate(borular, new Vector3(3, Random.Range(-height, height), 0), Quaternion.identity);
    }

}

}
ama bu kodub 13cü satırına hata veriyor hatada bu:
NullReferenceException: Object reference not set to an instance of an object
pipe_spawner+d__4.MoveNext () (at Assets/scripts/pipe_spawner.cs:19)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <3b24cc7fa9794ed8ab04312c53e6dedd>:0)
UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator)
biri yardım ederse sevinirim.

2

Unity inspector üzerinden public nesnelere atama yaptınız mı?

4

evet atadım kesinlikle eninim

5