IndexOutOfRangeException: Array Index is out of range Help

Hey, could someone help me solve this error in my script, saying:

IndexOutOfRangeException: Array index is out of range. MultipleWaypoints+$RotateTowards$88+$.MoveNext () (at Assets/Train/AItrainscripts/MultipleWaypoints.js:28) UnityEngine.MonoBehaviour:StartCoroutine_Auto(IEnumerator) MultipleWaypoints:Update() (at Assets/Train/AItrainscripts/MultipleWaypoints.js:21)

It occurs when my train model reaches the last waypoint. I do know its saying the error is at line 28, but i have no idea what to change or what the error actually is. Help would be appreciated.

This is the script:

var waypoint : Transform[];

var speed : float = 20;

private var currentWaypoint : int;

function Update () {

if(currentWaypoint < waypoint.length){

   var target : Vector3 = waypoint[currentWaypoint].position;

   var moveDirection : Vector3 = target - transform.position;  

   var velocity = rigidbody.velocity;

   

 if(moveDirection.magnitude <=1.0){

     currentWaypoint++;

 }

 else{

     velocity = moveDirection.normalized * speed;

     

 }

}

 rigidbody.velocity = velocity;

 RotateTowards();

}

function RotateTowards () {

var target : Vector3 = waypoint[currentWaypoint].position;

var moveDirection : Vector3 = target - transform.position;

 while(Vector3.Distance(target, transform.position) >= 1.5){





 transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation(moveDirection), 0.5* Time.deltaTime);





 transform.eulerAngles = new Vector3(0, transform.eulerAngles.y, 0);





 yield;





 }

}