Enemy Respawn causes player to unable to attack

Ok so when i attack and kill the enemy it respawns back to its starting position the only problem is im unable to fight it again i get this error

missingreferenceexception: the object of type 'gameobject' has been destroyed but you are still trying to Access it your script should either check if it is null or you should not destroy the object.

what is my problem?

here is the player attack script

 using System.Collections;

public class PlayerAttack : MonoBehaviour { public static GameObject target; public float attackTimer; public float Cooldown;

 void Awake(){
     
     target = GameObject.FindGameObjectWithTag("Enemy");    

 }

 // Use this for initialization
 void Start () {
     attackTimer = 0;
     Cooldown = 1.0f;
 
 }
 
 // Update is called once per frame
 void Update () {
     if(attackTimer > 0)
         attackTimer -= Time.deltaTime;
     
     if(attackTimer < 0)
         attackTimer = 0;
     
     if(Input.GetKeyUp(KeyCode.Mouse0)){
         if(attackTimer == 0){
             Attack();
             attackTimer = Cooldown;
         }
     }
 
 }
 
 private void Attack(){
     float distance = Vector3.Distance(target.transform.position, transform.position);
     
     Vector3 dir = (target.transform.position - transform.position).normalized;
     
     float direction = Vector3.Dot(dir, transform.forward);
     
     Debug.Log(direction);
     
     if(distance < 2.5f){
         if(direction > 0){
         EnemyHealth Health = (EnemyHealth)target.GetComponent("EnemyHealth");
         Health.AdjustCurrentHealth(-10);
         }
     }
 }

}