Problem with messenger extended

I am not sure, if it is correct to ask about the error with it here, but...

I get this error:

NullReferenceException Enemy.OnAttackReceived (Int32 Damage, Single Attack_Range, Single Attack_Spread) (at Assets/!Enemy/Enemy.cs:31) Messenger`3[System.Int32,System.Single,System.Single].Broadcast (System.String eventType, Int32 arg1, Single arg2, Single arg3, MessengerMode mode) (at Assets/_Scripts/_MessengerExtended/Messenger.cs .cs:212) Messenger`3[System.Int32,System.Single,System.Single].Broadcast (System.String eventType, Int32 arg1, Single arg2, Single arg3) (at Assets/_Scripts/_MessengerExtended/Messenger.cs .cs:203) Weapon_Meele_Default_Script.Attack () (at Assets/!Weapon/Weapon_Meele_Default_Script.cs:46) Weapon_Meele_Default_Script.Update () (at Assets/!Weapon/Weapon_Meele_Default_Script.cs:29)

With these two scripts: 1) using UnityEngine; using System.Collections;

 public class Weapon_Meele_Default_Script : MonoBehaviour 
 {
     public int Damage;
     public float Attack_Cooldown;
     public float Attack_Range;
     public float Attack_Spread;
     public GameObject WhatToDrop;
     private float Timer;
 
     void Update ()
     {
         if (Input.GetMouseButton (0)) 
         {Attack ();
         print ("Attack function launched");}

         while(Timer>0)
         Timer -= Time.deltaTime;
 
         if(Timer<0)
         Timer=0;
     }



     public void Attack()
     {
     Messenger<int, float, float>.Broadcast("AttackPlayer", Damage, Attack_Range, Attack_Spread);
         Timer = Attack_Cooldown;
         print ("We attacked");
     }
 }

2)

 using UnityEngine;
 using System.Collections;
 
 public class Enemy : MonoBehaviour 
 {
     public int MaxHealth = 100;
     public int CurHealth = 100;
     public GameObject Player;
     private Transform TEXTMESH;
 
 
 void Start ()
     {
     Messenger<int, float, float>.AddListener("AttackPlayer", OnAttackReceived);
     Player = GameObject.Find("Player");
 
     TEXTMESH = transform.Find("Health_Text");
     TEXTMESH.GetComponent<TextMesh>().text = (CurHealth.ToString() + "/" + MaxHealth.ToString());
 
     }
 
     public void OnAttackReceived (int Damage, float Attack_Range, float Attack_Spread)
     {
     float distance = Vector3.Distance (Player.transform.position, transform.position);
         
     Vector3 dir = (transform.position - Player.transform.position).normalized;
     float direction = Vector3.Dot(dir, Player.transform.forward);
         
     Debug.Log (direction);
         
     Debug.Log (distance);
     if (distance < Attack_Range) 
     { if(direction>Attack_Spread)
         {
         HealthAdjustment(Damage);
         }
     }
     }
 
 
     public void HealthAdjustment (int adj)
     {
     CurHealth += adj;
     TEXTMESH.GetComponent<TextMesh>().text = (CurHealth.ToString() + "/" + MaxHealth.ToString());
 
     print("Enemy got hurt");
 
     if(CurHealth < 0)
         CurHealth = 0;
     if(CurHealth>MaxHealth)
         CurHealth=MaxHealth;
     if(MaxHealth<1)
         MaxHealth=1;
 
     } 
 } 

Problem is, I can not decypher what this error means.