Object reference not set to an instance of an object?

Hi guys, I came up with this problem. I am using TairaGames' point to click tutorial.

Code (csharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SendInfo : MonoBehaviour
5. {
6.  
7.  
8.     void Start()
9.     {
10.  
11.     }
12.  
13.  
14.     void Update()
15.     {
16.  
17.         bool RMB = Input.GetMouseButtonDown(0);
18.  
19.         if (RMB)
20.         {
21.  
22.             RaycastHit hit;
23.             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
24.  
25.             if (Physics.Raycast(ray, out hit) && hit.transform.tag == "Ground")
26.             {
27.                 this.GetComponent<PhotonView>().RPC("RecievedMove", PhotonTargets.All, hit.point);
28.             }
29.  
30.  
31.         }
32.  
33.     }
34. }
35.  
36.  

There error is:
NullReferenceException: Object reference not set to an instance of an object SendInfo.Update () (At Assets/Scripts/SendInfo.cs:23)
I looked at like 23, and couldn't find anything wrong with it;

Code (csharp):

1.  
2.   Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
3.  

 

Do you have a camera with a tag "main camera"? (I'm pretty sure, that would give an error like "there is no camera tagged main camera")

 

Ah, that did the trick! thanks!

 

I don't want to discourage you, but you are still new, I really don't recommend to trying a muktiplayer game. Just try simple games and add more and more to them. I remember when I started, networking just went over my head lol. Just trying to help

 

I'm not necessarily 'new' to coding it's just I am new to unity. I use Photon for networking which finishes most of the network off, well to my knowledge. This is more of a test project to see what unity can do.

 

He meant new to unity too though

 

Ah okay, sorry for the misunderstanding