I have an error on line 5 “field AsteroidManager.asteroid is never assigned to, and will always have its default value null” I would like for Asteroid to be linked to the second public class Asteroid (second code). How can I solve the issue?

1 using System.Collections;
2 using System.Collections.Generic;
3 using UnityEngine;
4 public class AsteroidManager : MonoBehaviour {
5 [SerializeField] Asteroid asteroid;
7 [SerializeField]int gridSpacing = 10;
8
9 void Start()
10 {
11 PlaceAsteroids ();
12 }
13
14 void PlaceAsteroids()
15 {
16 for (int x = 0; x < gridSpacing; x++)
17 {
18 InstantiateAsteroid (x, 0, 0);
19 }
20 }
21 void InstantiateAsteroid(int x, int y, int z)
22 {
23 Instantiate(asteroid, transform.position, Quaternion.identity, transform);
24 }
25 }

I found the issue no worries!!