Возникает ошибка NullReferenceException: Object reference not set to an instance of an object DownMover.Update () (at Assets/DownMover.cs:20)

Возникает ошибка NullReferenceException: Object reference not set to an instance of an object DownMover.Update () (at Assets/DownMover.cs:20) в коде:

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

public class DownMover : MonoBehaviour
{
    public float speed;
    private Spawner spawner;
    private bool spawned;
    
    private void Start()   
    {
        spawner = FindObjectOfType<Spawner>();
        speed = spawner.speed;
    }

    private void Update()
    {
        transform.Translate(Vector2.down * speed * Time.deltaTime);
        speed += spawner.speedIncrease * Time.deltaTime;
        if(transform.position.y < 0 && !spawned)
        {

        }
    }
}

как можно исправить? Язык c#