using System.Collections;

using System.Collections.Generic;
using UnityEngine;

public class DroneMonitor_Trigger_Script : Photon.MonoBehaviour
{
public GameObject Drone;
public float Speed;
public bool HaveWeEnteredTrigger = false;
public Vector3 dir;

//=========================================================================  
[PunRPC]  
public void MoveDrone(Vector3 direction)  
{  
    Drone.transform.Translate(Vector3.up * Time.deltaTime * Speed);  
}

//=========================================================================  
public void OnTriggerEnter(Collider other)  
{  
    if(other.tag == "Player")  
    {  
        HaveWeEnteredTrigger = true;  
          
    }  
}

//=========================================================================  
  
// Update is called once per frame  
void Update ()  
{  
    if (Input.GetKey(KeyCode.Insert))  
    {  
        if (HaveWeEnteredTrigger == true)  
        {  
            dir = Vector3.up;  
            photonView.RPC("MoveDrone", PhotonTargets.MasterClient, dir);   
            // The above line is what is generating the error...  
            // NULLREFERENCEEXCEPTION: Object reference not set to an instance of an object.  
            // DroneMonitor_Trigger_Script.Update() (at Assets/DroneMonitor_Trigger_Script.cs:39)  
        }  
    }  
<img src="http://www.carpatheous.com/DroneWithCamera.png" alt="" />  

}
}