Can't clone if parent is destroyed

The object gets destroyed in play. It's a wave based PVE where enemies are spawned in randomly and the player swings their sword at them, destroying the game object.

I dragged the slime prefab directly from the asset folder into the Enemy Spawner parameter, and I am getting the same error.

NullReferenceException: Object reference not set to an instance of an object PlayerHealth.TakeDamage (System.Int32 amount, System.Single dmg) (at Assets/Scripts/PlayerHealth.cs:23) EnemyDamage.OnTriggerEnter2D (UnityEngine.Collider2D collider) (at Assets/Scripts/EnemyDamage.cs:25)

PlayerHealth Script:

     public class PlayerHealth : MonoBehaviour
     {
         public Image healthBar;
         public int realth;
         public int maxRealth = 100;
         public float healthAmount = 100f;
     
         // Start is called before the first frame update
         void Start()
         {
             realth = maxRealth;
         }
     // Update is called once per frame
     public void TakeDamage(int amount, float dmg) {
         realth -= amount;
         healthAmount -= dmg;
         healthBar.fillAmount = healthAmount / 100f;
         if (realth <= 0) {
             Destroy(gameObject);
         }
     }
 }

EnemyDamage Script:

 public class EnemyDamage : MonoBehaviour
 {
     public PlayerHealth playerHealth;
     public int damage = 1;
     public float dmg = 1;
     // Start is called before the first frame update
     void Start()
     {
 
     }
 
     // Update is called once per frame
     void Update()
     {
 
     }
     private void OnTriggerEnter2D(Collider2D collider)
     {
         if (collider.gameObject.tag == "Player")
         {
             playerHealth.TakeDamage(damage, dmg);
         }
     }
 }