Object reference is NULL when IT IS set to an instance of an object?

Currently I am trying to get my current object that contains a NavMeshAgent to move towards 3 different waypoints. When one waypoint is reached, the object will go to the next waypoint. I am receiving an error on the line that contains > agent.SetDestination (wayPoint [0].position);. Before this line I have already set my agent variable to the component attached to my current object so I am a little confused why this null reference exception is occurring. Thanks in advance.

using UnityEngine; using System.Collections;

 public class NPCmovement : MonoBehaviour {
     public GameObject player;
     public Transform[] wayPoint = new Transform[3];
     Vector3 dist;
     NavMeshAgent agent;
     // Use this for initialization
     void Start () {
         agent = GetComponent<NavMeshAgent> ();
     }
     
     void Update () 
     {
         agent.SetDestination (wayPoint [0].position);
         if (transform.position == wayPoint [0].position) {
             agent.SetDestination (wayPoint [1].position);
             //if(agent 
             if (transform.position == wayPoint [1].position) {
             
                 agent.SetDestination (wayPoint [2].position);
 
             }
         }

}