Object reference not set to an instance of an Object C#

Im trying to make a multiplayer game, but the code that i am using brings up the error "Object reference not set to an instance of an Object". How can i fix this?

My Code:

using UnityEngine;
using System.Collections;

public class FP_Shooting : MonoBehaviour {

public GameObject bullet_prefab;
float bulletImpulse = 50f;
float delay = 0;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void FixedUpdate () {
if (networkView.isMine) {
if (Input.GetButtonDown ("Fire1") && delay <= Time.time) {
Camera cam = Camera.main;
GameObject thebullet = (GameObject)Instantiate (bullet_prefab, cam.transform.position + cam.transform.forward, cam.transform.rotation);
thebullet.rigidbody.AddForce (cam.transform.forward * bulletImpulse, ForceMode.Impulse);
delay = Time.time + 0.1f;
}
}
}
}

 

The error that I am getting is:

NullReferenceException: Object reference not set to an instance of an object Shoot.FixedUpdate () (at Assets/Scripts/Shoot.cs:21)

 

When I change the networkView.isMine to NetworkView.isMine, it stops me from running the game and says this:

Assets/Scripts/FP_Shooting.cs(17,33): error CS0120: An object reference is required to access non-static member `UnityEngine.NetworkView.isMine'

 

yes, the prefab is connected up to the bullet