gameObject.BroadcastMessage error

My health system doesn't work. It is supposed to deal damage to the player every .5 seconds that the enemy "colliding" with the player (using distance to determine if they are close together for simplicity).

Problem is that I'm getting a NullReferenceException (Object reference not set to an instance of an object MobBehaviour.Attack () (at Assets/Scripts/MobBehaviour.js:35)).

 var health : int = 25;
 var damage : int = 10;
 var attackSpeed : float = 0.5;
 var gravity : float = 30.0;
 var target : GameObject;
 
 private var moveDirection : Vector3 = Vector3.zero;
 private var nextAttack : float = 0.0;
 
 function Update () {
     var controller : CharacterController = GetComponent(CharacterController);
     if(Vector3.Distance(transform.position, target.transform.position) <= 1.1){
         Attack();
     }
     // Apply gravity
     moveDirection.y -= gravity * Time.deltaTime;
     controller.Move(moveDirection * Time.deltaTime);
 }
 
 function ApplyDamage (damage : int) {
     health -= damage;
 
     if(health <= 0) {
         Destroy(gameObject);
     }
 }
  
  function Attack(){
     if(Time.time > nextAttack){
         nextAttack = Time.time + attackSpeed;
         target.BroadcastMessage("ApplyDamage", damage, SendMessageOptions.DontRequireReciever);
     }
  }

I have used gameObject.BroadcastMessage before without any problems, but this time I just can't get it work for some reason.