NullReferenceException: Object reference not set to an instance of an object

so i have a an enemy in a room. i only want the enemy to move and attack when the player is in the room so i have put a trigger on the floor with this script:
using UnityEngine;
using System.Collections;

public class trigger : MonoBehaviour {
	
	
	// Use this for initialization
	void Start () {
			
	}
	
	// Update is called once per frame
	void OnTriggerEnter (Collider Player) {
		if (Player.CompareTag("Player")){
			Debug.Log (Player.gameObject.name);
			
			attackScript.Attack();
		}
	}
}

then i have this script attached to my enemy:
using UnityEngine;
using System.Collections;

public class attackScript : MonoBehaviour {
	
	public Transform target;
	public static attackScript attack;
	// Use this for initialization
	void Start () {
	//	Transform me = transform;
	}
	
	// Update is called once per frame
	public static void Attack() {
		attack.StartAttack();
	}
	void StartAttack(){
		animation.Play ("intmidate");
		transform.LookAt(target);
	}
}

but i get this error:
NullReferenceException: Object reference not set to an instance of an object

i get it for this line of script:
attack.StartAttack();

any ideas how to fix this?

initialize attack with " public static attackScript attack = this;"