rpg enemy target gives null reference

after giving my enemy a target it shows a null reference in the editor, it seems to be in line 90

 if (HeroToAttack.GetComponent<HeroSM>() != null)
          {
              DoDamage();
          }

line that i added only to avoid any null reference that will show in line 105

 HeroToAttack.GetComponent<HeroSM>().TakeDamage(calcDamage);

the idea is that my enemy gets a random target from the heroes performing list, i do this using state machines.

here is the one of the enemy:

using UnityEngine; using System.Collections; using UnityEngine.UI;

public class EnemySM : MonoBehaviour {

  public EnemyStats Enemy;//creamos a enemigo desde la plantilla
  private BattleState BS;
  public bool actionStarted = false;
  public GameObject Description;
  private HandleTurn myAttack;
 
  public enum enemyTurn
  {
      PROCESSING,
      CHOOSEACTION,
      WAITING,
      ACTION,
      DEAD
  }
  public static enemyTurn currentEnemyTurn;
  private float curCooldown = 0f;
  private float maxCooldown = 8f;
 
  //para cambiar las barras
  private float curHealth;
  public GameObject HeroToAttack;
  // Use this for initialization
  void Start()
  {
      myAttack = new HandleTurn();
      currentEnemyTurn = enemyTurn.PROCESSING;
      BS = GameObject.Find("BM").GetComponent<BattleState>();
 
  }
  // Update is called once per frame
  void Update()
  {
 
         
      if (GMScript.InBattle == true)
      {            
          curHealth = Enemy.CurrentHp;
          switch (currentEnemyTurn)
          {
              case (enemyTurn.PROCESSING):
                  UpgradeBar();
                  break;
              case (enemyTurn.CHOOSEACTION):
                  //print("enemy chooseaction");
                  ChooseAction();
                  currentEnemyTurn = enemyTurn.WAITING;
 
                  break;
              case (enemyTurn.WAITING):
                  //idle state                   
                  break;
              case (enemyTurn.ACTION):
                 // print("enemy action");
                  StartCoroutine(TimeForAction());
 
                  break;
              case (enemyTurn.DEAD):
                  break;
          }
      }
  }
 
 
 
  void ChooseAction()
  {
      myAttack = new HandleTurn();
      myAttack.Attacker = Enemy.baseName;
      myAttack.Side = "Enemy";
      myAttack.AttackerGO = this.gameObject;
      myAttack.TargetGO = BS.HeroInGame[Random.Range(0, BS.HeroInGame.Count)];
      HeroToAttack = myAttack.TargetGO;
      int num = Random.Range(0, Enemy.Attacks.Count);//se genra un numero aleatorio entre 0 y la cantidad de ataques
      myAttack.chooseAttack = Enemy.Attacks[num];//usamos el numero para escoger el ataque
      Debug.Log(this.gameObject.name + " has choosen " + myAttack.chooseAttack.attackName + " and did " + myAttack.chooseAttack.attackDamage + " damage!!!");
      BS.CollectActions(myAttack);
  }
  private IEnumerator TimeForAction()//controla variables atraves del tiempo
  {
      
      if (actionStarted == true)
      {
          yield break;
      }
      actionStarted = true;
      //wait
      //do damage
      
      if (HeroToAttack.GetComponent<HeroSM>() != null)
      {
          DoDamage();
      }
          //remove from bs list
      BS.PerformList.RemoveAt(0);//remueve al objeto en 0, el siguiente sube transformando el 1 en 0
                                 //continua removiendo hasta desaparecer todo
                                 //reset bs to wait
      BS.battleStates = BattleState.performAction.WAIT;
      //al pasar a wait y saltar a takeaction los objetos vuelven a crearse repitiendo el ciclo
      //end coroutine
      actionStarted = false;
      currentEnemyTurn = enemyTurn.PROCESSING;
  }
  void DoDamage()
  {
      float calcDamage = Enemy.Fue * BS.PerformList[0].chooseAttack.attackDamage;
      print(calcDamage);
      HeroToAttack.GetComponent<HeroSM>().TakeDamage(calcDamage);
  }
 
  void UpgradeBar()
  {
      print(curCooldown);
      curCooldown = curCooldown + Time.deltaTime;
      if(curCooldown >= maxCooldown)
      {
          currentEnemyTurn = enemyTurn.CHOOSEACTION;
          curCooldown = 0f;
      }
  }
 

}

kind of a long script, i think the place to check is in the do damage or timeforaction functions but cant seem to find anything.