Issues with GameObject List in NetworkManager Unet HLAPI.

Hello. I am creating a ranking match for the player´s score in the match. My problem is : The score int variable is into the class which contains the player attributes. When a client starts game and the player prefab is instantiated is added to a GameObject List. But when that client disconnects i have a lot reference errors. So i would need to destroy the gameObject into the GameObjects List when the clients disconnects. I have tried many ways and nothing. The errors are coming because the sorting class for the List is trying to acces it and can´t find the gameObject that was destroyed. Here i show my code. Thank you.

C# Code

public class RankingMatch : NetworkBehaviour

{ [SerializeField] List zombies = new List(); [Header("Time Variables")] [SerializeField] private float time; [SerializeField] private float nextcomunicationTime = 1f; [SerializeField] private float comunicationTime;

 void Start()
 {

 }

 void Update()
 {
     time = GameObject.Find("NetworkManager").GetComponent<CustomNetworkManager>().time;

     if (time >= comunicationTime)
     {
         if (zombies.Count >= 2)
         {
             zombies.Sort(new sort());
             
         }
         comunicationTime = Time.time + nextcomunicationTime;
     }
 }

 public void AddZombie(GameObject zombie)
 {
     zombies.Add(zombie);
 }


 private class sort : IComparer<GameObject>
 {
     int IComparer<GameObject>.Compare(GameObject _objA, GameObject _objB)
     {
         int t1 = _objA.GetComponent<ZombieAttributes_Net>().zombieScore;
         int t2 = _objB.GetComponent<ZombieAttributes_Net>().zombieScore;
         return t1.CompareTo(t2);
     }
 }

 

}