How to Make Enemy Attack When In Range of The Player?

So my game is a 2D top down movement game and my script does make my enemy attack but it constantly loops the attack animation because I obviously don't know what EXACTLY to put code wise to make the enemy attack when in range of the player to do damage instead of letting him constantly loop. Also i seem to be getting an error when i get close to my enemy as of right now it says

NullReferenceException: Object reference not set to an instance of an object EnemyCombat.Attack () (at Assets/EnemyCombat.cs:36) EnemyCombat.Update () (at Assets/EnemyCombat.cs:25) Link

Also, Here is the EnemyCombat script

Code (CSharp):

1.  
2.    enemy attausing System.Collections;
3.    using System.Collections.Generic;
4.    using UnityEngine;
5.  
6.    public class EnemyCombat : MonoBehaviour
7.    {
8.        public Animator animator;
9.  
10.        public Transform AttackPoint;
11.  
12.        public float attackRange = 0.5f;
13.  
14.        public LayerMask enemyLayers;
15.  
16.        public int attackDamage = 5;
17.  
18.        public float attackRate = 2f;
19.        float nextAttackTime = 0f;
20.  
21.        // Update is called once per frame
22.        void Update()
23.        {
24.            if (Time.time >= nextAttackTime)
25.            {
26.                Attack();
27.                nextAttackTime = Time.time + 1f / attackRate;
28.            }
29.        }
30.  
31.        void Attack()
32.        {
33.            animator.SetTrigger("Attack");
34.            Collider2D[] hitEnemies = Physics2D.OverlapCircleAll(AttackPoint.position, attackRange, enemyLayers);
35.            foreach (Collider2D enemy in hitEnemies)
36.            {
37.                enemy.GetComponent<Enemy>().TakeDamage(attackDamage);
38.            }
39.        }
40.  
41.        void OnDrawGizmosSelected()
42.        {
43.            if (AttackPoint == null)
44.                return;
45.  
46.            Gizmos.DrawWireSphere(AttackPoint.position, attackRange);
47.        }
48.    }

 

Code (csharp):

1.  
2. enemy.GetComponent<Enemy>().TakeDamage(attackDamage);
3.  

What do you think is going to happen when some of the objects you got have no "Enemy" components on them?