C# GameObject Lists

Hi im using a list in C# to list all of my game objects in unity so that i can select them, but when i destroy those game objects im not able to select the rest of the objects because the gameobect was destroyed. can anyone help me?

ok this is my targeting code

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class targetting : MonoBehaviour {
     public List<Transform> targets;
     public Transform selectedTarget;
     private Transform myTransform;
     
         
     // Use this for initialization
     void Start () {
     targets = new List<Transform>();
         selectedTarget = null;
         myTransform = transform;
         AddAllEnemies();
         
     }
     public void AddAllEnemies(){
     GameObject[]go = GameObject.FindGameObjectsWithTag("Enemy");    
         foreach(GameObject enemy in go)
             AddTarget(enemy.transform);
     }
     public void AddTarget(Transform enemy){
     targets.Add(enemy);    
         
     }
     private void SortTargetsByDistance(){
         
         targets.Sort(delegate(Transform t1, Transform t2) { 
             return Vector3.Distance(t1.position, myTransform.position).CompareTo(Vector3.Distance(t2.position, myTransform.position));
                 });
     }
     private void targetEnemy (){
             if(selectedTarget == null)
             {
                 SortTargetsByDistance();
                 selectedTarget = targets[0];
             }
         else
         {
         int index = targets.IndexOf(selectedTarget);
             if(index < targets.Count-1)
             {
                 index++;
             }
             else
             {
             index = 0;    
             }
             DeselectTarget();
             selectedTarget = targets[ index ];
             
         }
         SelectTarget();
         if(selectedTarget == null){
             SortTargetsByDistance();
             selectedTarget = targets[1];
         }
     }
     private void SelectTarget(){
     selectedTarget.renderer.material.color = Color.red;    
         PlayerAttack pa = (PlayerAttack)GetComponent("PlayerAttack");
         pa.target = selectedTarget.gameObject;
     }
     private void DeselectTarget()
     {
     selectedTarget.renderer.material.color = Color.blue;
         selectedTarget = null;    
             
     }
     // Update is called once per frame
     void Update () {
     if(Input.GetKeyDown(KeyCode.Tab)){
             targetEnemy();
             
             
         }
     }
     private void deselectTargets(){
     
     }
 }
 

and this is the health script that applies the destroyed object ( by the way i just used gameobject(destroy))

 using UnityEngine;
 using System.Collections;
 
 public class EnemyHealth : MonoBehaviour {
     public int maxHealth = 100;
     public int curHealth = 100;
     
     
     public float healthBarLength;
     // Use this for initialization
     void Start () {
         healthBarLength = Screen.width /2;
     }
     
     // Update is called once per frame
     void Update () {
     AddjustCurrentHealth(0);
         
     }
     void OnGUI(){
         
     if(curHealth <= 0){
     GUI.Box(new Rect(Screen.width /2.1f, Screen.height /2.1f, 100, 25), "you are dead");
             Time.timeScale = 0;
             
     }
     GUI.Box(new Rect(10, 40, healthBarLength, 20), curHealth + "/" + maxHealth);    
         
     if(curHealth <= 0){
         gameObject(Destroy);
         }
     
 }
     public void AddjustCurrentHealth(int adj) {
         
     curHealth += adj;
     if(curHealth <0)
         curHealth = 0;
     if(curHealth > maxHealth)
         curHealth = maxHealth;
     if(maxHealth < 1)
         maxHealth = 1;
     healthBarLength = (Screen.width /2) * (curHealth /(float)maxHealth);        
     }
     
     void Die(){
     
         transform = 0;
         
     }
 }