Null reference exception when calling Remote Procedure Call

Below is my NetworkBehaviour script which is attached to a GameObject in the scene for all players and the TriggerGameStart is called just fine but calling RpcStartGame gives me a null reference exception (line 9) and I can't see why this might be when it's part of the same script.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using UnityEngine.Networking;
4.  
5. public class NetworkController : NetworkBehaviour
6. {
7.     public void TriggerGameStart()
8.     {
9.         RpcStartGame();
10.     }
11.  
12.     [ClientRpc]
13.     void RpcStartGame()
14.     {
15.         UIController.Instance.StartGame ();
16.     }
17. }

Any suggestions will be greatly appreciated.

 

This might sound a little silly, but have you tried adding

if(!isServer)
return;

just before the RPC? Just a thought

 

It should only be called by the server because that's determined in the script which calls TriggerGameStart, but I added that anyway. Now the null reference exception is triggered when doing

Code (CSharp):

1. if(!isServer)

This would imply that the gameobject itself is null but then how do I manage to call TriggerGameStart in the first place?