how to stop agent when target is unreachable unity

hello everybody

i want my player characters stop when target is unreachable.

plaese watch this video.

as you can see in this video, the agents don't stop when target is unreachable

and this is my simple code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.AI;
 using UnityStandardAssets.Characters.ThirdPerson;
 
 public class PlayerController : MonoBehaviour {
     public Camera cam;
 
     public NavMeshAgent agent;
 
     public ThirdPersonCharacter character;
 
     private LineRenderer linerenderer;
     
     bool isMoving = true;
     // Start is called before the first frame update
     void Start()
     {
         agent.updateRotation = false;
         linerenderer = GetComponent();
     }
 
     Vector3 hitPos = Vector3.zero;
     // Update is called once per frame
     void Update()
     {
         if (Input.GetMouseButtonDown(0)) {
             Ray ray = cam.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit;
 
             if (Physics.Raycast(ray, out hit)) {
                 agent.destination = (hit.point);
                 hitPos = hit.point;
             }
         }
 
         if (agent.path.status == NavMeshPathStatus.PathInvalid || agent.path.status == NavMeshPathStatus.PathPartial) {
             character.Move(Vector3.zero, false, false);
             agent.velocity = Vector3.zero;
             agent.isStopped = true;
             agent.ResetPath(); 
             linerenderer.enabled = false;
         } else {
             character.Move(agent.desiredVelocity, false, false);
 
             linerenderer.positionCount = agent.path.corners.Length;
             linerenderer.SetPositions(agent.path.corners);
             linerenderer.enabled = true;
         }
     } }