IEnumerator keeps saying not all code paths return values

on the IEnumerator hitting Its saying not all code paths return a value I'm so confused I'm doing the same as everyone else please tell me what I did wrong!!!

public class BasicAI : MonoBehaviour {

 private NavMeshAgent agent;
 private Animator Animator;

 public float Health = 200;
 public float DistanceToHit;
 public float Damage;

 public bool Chase;
 private bool IsChasing;
 public bool Wander;
 public bool PickWander;
 public bool Dead = false;
 public bool CanHit = false;
 public bool Touching = false;
 public bool Hit = false;
 public bool hitting = true;

 private Transform PlayerTransform;
 public Transform WanderRight;
 public Transform WanderLeft;
 public Transform WanderForward;
 public Transform WanderBackward;
 public Transform WanderStay;
 public Transform WanderPlace;
 private float HowFarFromPlayer;

 // Use this for initialization
 void Start () {
     Animator = GetComponent<Animator>();
     agent = GetComponent<NavMeshAgent>();
 }
 private void OnCollisionStay(Collision collision)
 {
     if (collision.collider.GetComponent<Player>())
     {
         if (Dead == false)
         {
             collision.collider.GetComponent<Player>().health -= 20;
             Touching = true;
             CanHit = true;
         }
     }
 }
 private void OnCollisionExit(Collision collision)
 {
     if (collision.collider.GetComponent<Player>())
     {
         Touching = false;
         CanHit = false;
     }
 }
 private void OnTriggerEnter(Collider target)
 {
     if (target.GetComponent<Player>())
     {
         PlayerTransform = target.transform;
         IsChasing = true;
         
     }
 }
 private void OnTriggerExit(Collider target)
 {
     if (target.GetComponent<Player>())
     {
         PlayerTransform = null;
         IsChasing = false;
     }
 }
   
 IEnumerator Hitting()
 {

 }
 void Update () {
     Animator.SetBool("Walk", IsChasing);
     Animator.SetBool("Die", Dead);
     if (PlayerTransform != null)
     {
         HowFarFromPlayer = Vector3.Distance(gameObject.transform.position, PlayerTransform.transform.position);
     }
     //Health Die 
     if(Hit == true)
     {
         hitting = true;
         StartCoroutine(Hitting());
     }
     if (IsChasing == true)
     {
        
             if (HowFarFromPlayer <= DistanceToHit)
             {
                 Hit = true;
             }
         
     }
     if (Health <= 0)
     {
         IsChasing = false;
         Dead = true;
         agent.SetDestination(gameObject.transform.position);
         Destroy(gameObject,3);
     }
     if(IsChasing == false)
     {
         agent.SetDestination(gameObject.transform.position);
     }
     if(IsChasing == true)
     {
         agent.SetDestination(PlayerTransform.transform.position);
     }
 }

}