getting error with networkView

hi, again i'm trying to make a script used for apply damage to other players online but i'm getting this error"NullReferenceException: Object reference not set to an instance of an object controladorTaijutsu.aplicar (NetworkViewID id) (at Assets/MMOAsset/ScriptJugador/Taijutsu/controladorTaijutsu.js:173)" heres the code

 function OnTriggerStay(otro : Collider)
 {
                 if(otro.gameObject.tag == "Player")
                 {
                     if(otro.GetComponent(MovimientoJugadorBasico)){                        
                         if(modoAtaque){
                         if((Input.GetButtonUp("punch")  || Input.GetButtonUp("kick")))
                         
                         //otro.GetComponent(MovimientoJugadorBasico).recibirAtaque(modoAtaque,hit);
                         var viewID = otro.collider.networkView.viewID;
                         networkView.RPC("aplicar",RPCMode.All,viewID);                        
                         }
                         otro.GetComponent(MovimientoJugadorBasico).herido = modoAtaque;
                     }
                 }
 }

this is the function called by the RPC

 @RPC
 function aplicar(id : NetworkViewID)
 {
     var enID = NetworkView.Find(id);
     var en = enID.observed.gameObject; // this is the error line
     en.gameObject.SendMessageUpwards("recibirAtaque",hit,SendMessageOptions.DontRequireReceiver);
 }

thanks