Error

using UnityEngine;
using System.Collections;

public class Menu : MonoBehaviour {

	private string CurMenu;
	public string Name;
	public string MatchName;
	public int Players;
	// Use this for initialization
	void Start () {
		CurMenu = "Main";
		Name = PlayerPrefs.GetString("PlayerName");
	}

	// Update is called once per frame
	void Update () {

	}

	void ToMenu(string menu){
		CurMenu = menu;
	}
	void OnGUI(){
		if (CurMenu == "Main")
			Main();
		if (CurMenu == "Host")
			Host();
		if (CurMenu == "Lobby")
			Lobby();
		if (CurMenu == "List")
			MatchList();
	}
	private void Main(){
		//if (GUI.Button(new Rect (0, 0, 128, 32), "Host A Match")) {
		// ToMenu ("Host");
		//}
		if (GUI.Button (new Rect (0, 0, 128, 32), "Host a match")) {
			ToMenu ("Host");
		}
		Name = GUI.TextField (new Rect (130, 0, 128, 32), Name);
		if (GUI.Button(new Rect (260, 0, 128, 32), "Save"))
			PlayerPrefs.SetString ("PlayerName", Name);
		if (GUI.Button(new Rect (0, 33, 128, 32), "Server List")){
			ToMenu ("List");
		}


	}

      private void Host(){
		if(GUI.Button(new Rect(0,0,128,32),"Start")){
			NetworkManager.Instance.StartServer(MatchName,Players);
			ToMenu("Lobby");
		}

		if(GUI.Button(new Rect(0,33,128,32),"Back")){
			ToMenu("Main");
		}
		MatchName = GUI.TextField(new Rect(130,0,128,32),MatchName);
		GUI.Label(new Rect(260,0,128,32),"Match name");
		Players = Mathf.Clamp(Players,2,8);
		GUI.Label(new Rect(260,32,128,32),"Amount Of Players");
		if (GUI.Button (new Rect (145, 32, 32, 32),"+"))
			Players ++;
		GUI.Label (new Rect (192, 33, 64, 32), Players.ToString());
		if (GUI.Button (new Rect (215, 33, 32, 32),"-"))
			Players --;
	}

	private void Lobby(){
		if(GUI.Button(new Rect(Screen.width - 128,Screen.height - 64,128,32),"Start")){

		}

		if(GUI.Button(new Rect(Screen.width - 128,Screen.height - 32,128,32),"Back")){
			ToMenu("Host");
		}

		GUILayout.BeginArea (new Rect(0, 0, Screen.width / 2, Screen.height));
		foreach(Player pl in NetworkManager.Instance.PlayerList)
		{
			GUILayout.Label(pl.PlayerName);
		}
		GUILayout.EndArea ();
	}
	private void MatchList()
	{
		if (GUI.Button(new Rect(0,0,128,32), "Refresh"))
		{
			MasterServer.RequestHostList("Tut");
		}
		if (GUI.Button(new Rect(0,33,128,32), "Back"))
		{
			ToMenu ("Main");
		}
		GUILayout.BeginArea(new Rect(Screen.width/ 2, 0, Screen.width / 2, Screen.height), "Server List","box");
		foreach (HostData hd in MasterServer.PollHostList())
		{
			GUILayout.BeginHorizontal();
			GUILayout.Label(hd.gameName);
			if(GUILayout.Button ("Connect"))
			{
				Network.Connect(hd);
				ToMenu("Lobby");
			}
			GUILayout.EndHorizontal();
		}
		GUILayout.EndArea();
	}
}