IndexOutOfRangeException: Array index is out of range.

Hey all! So halfway into development of this game, I got this error that I just can't solve. I'm super new to C# as well so I might have written some unnecessary super long codes that could have been done in a single line. I'm getting there.. hopefully. I've been tested for a day. sometime it run perfectly but sometime it gaves me errors. But i guess, there is nothing wrong for code. What i did is this.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Unit : MonoBehaviour {
 
     public GameObject Abintang;
     public Pathfinding pathfinding;
 
     public Transform target;
     private float speed = 5;
     private Vector3[] path;
     private int targetIndex;
     private bool checkSet;
 
 
     public bool pathPending{
         get{ 
             return pathfinding.requestManager.isProcessingPath;
             //return m_pathPending;
         }
     }
 
     public bool hasPath{
         get{
             return pathfinding.m_hasPath;
         }
     }
 
     public Vector3 destination{
         get{ 
             if (pathfinding.requestManager.isProcessingPath){
                 return pathfinding.m_destination;
             }
             if (path.Length == 0){
                 return transform.position;
             }
             if (pathfinding.grid == null){
                 return Vector3.positiveInfinity;
             }
             return pathfinding.m_destination;
         }
         set{ 
             if (target != null) {
                 pathfinding.m_destination = target.position;
             }
             pathfinding.m_destination = value;
         }
     }
 
     public float remainingDistance{
         get{ 
             if (pathfinding.m_destination != null){
                 return Vector3.Distance( pathfinding.m_destination , transform.position );
             }
         }
     }
 
 
     public bool isStopped{
         get{
             return pathfinding.m_isStopped;
         }
         set{ 
             pathfinding.m_isStopped = value;
         }
     }
 
     public float stoppingDistance { 
         get {
             return pathfinding.m_stoppingDistance;
         } 
         set {
             if (isStopped) {
                 pathfinding.m_stoppingDistance = Vector3.Distance (pathfinding.m_destination, transform.position);
             }
         }
     }
 
     void Start(){
         pathfinding = Abintang.GetComponent<Pathfinding> ();
         //PathRequestManager.RequestPath (transform.position, target.position, OnPathFound);
     }
 
     void Update(){
         if (checkSet) {
             PathRequestManager.RequestPath (transform.position, pathfinding.m_destination , OnPathFound);
         }
 
 
         if (target != null) {
             if (Vector3.Distance (transform.position, target.position) > 1f) {
                 SetDestination (target.position);
             }
         }
     }
 
     public void OnPathFound(Vector3[] newPath,bool pathSuccessful){
         if (pathSuccessful) {
             path = newPath;
             Debug.Log ("Path Length = " + path.Length.ToString ());
             StopCoroutine ("FollowPath");
             StartCoroutine ("FollowPath");
         }
     }
 
     IEnumerator FollowPath(){
         Vector3 currentWaypoint = path [0];
         targetIndex = 0;
 
         while (true) {
             if (transform.position == currentWaypoint) {
                 targetIndex++;
                 Debug.Log ("Target Index = " + targetIndex.ToString ());
                 if (targetIndex >= path.Length) {
                     yield break;
                 }
                 currentWaypoint = path [targetIndex];
             }
             transform.LookAt (currentWaypoint);
             print ("current waypoint : " + currentWaypoint.ToString ());
             transform.position = Vector3.MoveTowards (transform.position, currentWaypoint, speed * Time.deltaTime);
             checkSet = false;
             //Debug.Log ("CheckSet = False");
 
             yield return null;
         }
     }
 
     public void OnDrawGizmos(){
         if (path != null) {
             for (int i = targetIndex; i < path.Length; i++) {
                 Gizmos.color = Color.black;
                 Gizmos.DrawCube (path [i], Vector3.one);
 
                 if (i == targetIndex) {
                     Gizmos.DrawLine (transform.position, path [i]);
                 } else {
                     Gizmos.DrawLine (path [i - 1], path [i]);
                 }
             }
         }
     }
 
     public bool SetDestination( Vector3 _target){
         if (_target != null) {
             pathfinding.m_destination = _target;
             checkSet = true;
             Debug.Log ("CheckSet = true");
             print ("SetDestination = " + _target.ToString());
             return true;
         } else {
             checkSet = false;
             return false;
         }
     }
 
     public void Stop(){
         StopCoroutine ("FollowPath");
         pathfinding.m_isStopped = true;
     }
 
     public void Resume(){
         PathRequestManager.RequestPath (transform.position, pathfinding.m_destination, OnPathFound);
         //StopCoroutine ("FollowPath");
         //StartCoroutine ("FollowPath");
         pathfinding.m_isStopped = false;
     }
     public void HasReachedDestination(){
         if (Vector3.Distance (transform.position, pathfinding.m_destination) < 0.10f) {
             checkSet = false;
             Debug.Log ("CheckSet = False");
         }
     }
 
     public void ResetPath(){
         System.Array.Resize (ref path, 0);
     }
 }
 

and the error point to this line

 Vector3 currentWaypoint = path [0];

Thanks for taking out the time to help me out! :)