LeftHand Placement weapon manager

I have some problems with ik left hand placement unity explotes with mi c# code:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 [RequireComponent(typeof(Animator))]
 public class ControladorArma : MonoBehaviour
 {
     float IKweight=1.0f;
     private int armaActual = 0;
     Animator anim;
     [Header("Inventario")]
     public List<Arma> armas = new List<Arma>();//lista de armas
 
     [Header("posicionesIKArmas")]
     public List<GameObject> PosManoIzquierda = new List<GameObject>();//lista de manoizquierda
 
     [Header("Ubicaciones de Equipamento")]
     public List<Transform> equipado = new List<Transform>();// lista de equipado para cada arma 
     public List<Transform> Desequipado = new List<Transform>();//lista de desequipado para cada arma 
 
     // Use this for initialization
     void Start()
     {
         anim = GetComponent<Animator>();
     }
 
     // Update is called once per frame
     void Update()
     {
         //IKweight = Mathf.MoveTowards(IKweight, (UserInput.user.aim) ? 1.0f : 0.0f, Time.deltaTime * 5);//asigna valor del peso del ikweight matematicamente
         if (Input.GetKeyDown("1"))
         {
             cambiarArma();
         }
     }
 
     void OnAnimationIK()
     {
         anim.SetIKPositionWeight(AvatarIKGoal.LeftHand, IKweight);
         anim.SetIKRotationWeight(AvatarIKGoal.LeftHand, IKweight);
         Vector3 posicion = PosManoIzquierda[armaActual].transform.TransformDirection(Vector3.zero);
         //anim.SetIKPosition(AvatarIKGoal.LeftHand, PosManoIzquierda[armaActual].transform.position);
         //anim.SetIKRotation(AvatarIKGoal.LeftHand, PosManoIzquierda[armaActual].transform.rotation);
     }
 
     void cambiarArma() {
         armas[armaActual].gameObject.SetActive(false);
         do
         {
             armaActual = (armaActual + 1) % armas.Count;
         } while (!armas[armaActual].IsOwned());
         armas[armaActual].gameObject.SetActive(true);
     }
 }
 

and the Arma script is this: using UnityEngine; using System.Collections;

 public class Arma : MonoBehaviour {
     [SerializeField]
     //int municionTotal;
     public int municion = 0;
     public int cartucho = 0;
     int damage;
     int velDisparo;
     int cargador;
     public bool sw = false;
     private bool enPropiedad;
 
     void Start()
     {
         if (this.gameObject.name.Equals ("M4A1")) {
             //municionTotal = 120;
             municion = 30;
             cartucho = 90;
             Camera.main.GetComponent<PlayerGUI>().Municion = "30";
             Camera.main.GetComponent<PlayerGUI>().Cartucho = "90";
             sw = true;
         }
 
     }
     public int Municion {
         get {
             return this.municion;
         }
         set {
             municion = value;
         }
     }
 
     public int Cartucho {
         get {
             return this.cartucho;
         }
         set {
             cartucho = value;
         }
     }
     public bool Sw {
         get {
             return this.sw;
         }
         set {
             sw = value;
         }
     }
     //en propiedad
     public bool IsOwned()
     {
 
         return enPropiedad;
 
     }
 
     public void Owned()
     {
 
         enPropiedad = true;
 
     }
 }