NullReferenceException - With Network PlayerSpawn

Going to Change the Level after Creating the Server and then Spawn the Player. Anyway Error Output says:

    NullReferenceException
     UnityEngine.Network.Instantiate (UnityEngine.Object prefab, Vector3 position, Quaternion rotation, Int32 group) (at C:/BuildAgent/work/d3d49558e4d408f4/artifacts/EditorGenerated/Networking.cs:627)
     NetworkManager.SpawnPlayer () (at Assets/ColloseumNew/Scripts/NetworkManager.cs:54)
     NetworkManager.OnMasterServerEvent (MasterServerEvent masterServerEvent) (at Assets/ColloseumNew/Scripts/NetworkManager.cs:28)

The Code Line is where the "**" Ends and Starts.

 using UnityEngine;
 using System.Collections;
 
 public class NetworkManager : MonoBehaviour 
 {
     string registeredGameName = "Colloseum_Unique";
     bool isRefreshing = false;
     float refreshRequestLength = 5.0f;
     HostData[] hostData;
 
     private void StartServer ()
     {
         Network.InitializeServer (16, 25002, false);
         MasterServer.RegisterHost (registeredGameName, "Colloseum_Unique", "Test Implementation of Server Code");
     }
 
     void OnServerInitialized()
     {
         Debug.Log ("Server has been installed!");
     }
 
     void OnMasterServerEvent(MasterServerEvent masterServerEvent)
     {
         **if (masterServerEvent == MasterServerEvent.RegistrationSucceeded) 
         {
             Debug.Log ("Registration Succeed.");
             Application.LoadLevel("ColloseumMain");
             SpawnPlayer ();
         }**
     }
 
     public IEnumerator RefreshHostList()
     {
         Debug.Log ("Refreshing...");
         MasterServer.RequestHostList (registeredGameName);
         float timeEnd = Time.time + refreshRequestLength;
 
         while (Time.time < timeEnd) {
 
                         hostData = MasterServer.PollHostList ();
                         yield return new WaitForEndOfFrame ();
                 }
 
         if (hostData == null || hostData.Length == 0) {
                         Debug.Log ("No Active Servers has been found.");
                 } else { 
                         Debug.Log (hostData.Length + " has been found.");
                 }
     }
 
     private void SpawnPlayer()
     {
         Debug.Log ("Spawning Player...");
         Network.Instantiate (Resources.Load ("Prefabs/SamplePlayer"), new Vector3 (0f, 2.5f, 0f), Quaternion.identity, 0);
     }
 
     public void OnGUI()
     {
         if (Network.isClient || Network.isServer)
             return;
 
         if(GUI.Button(new Rect(25f, 25f, 150f, 30f), "Start New Server"))
         {
             StartServer ();
         }
 
         if(GUI.Button (new Rect(25f, 65f, 150f, 30f), "Refresh Server List"))
         {
             StartCoroutine("RefreshHostList");
         }
 
         if (hostData != null) 
         {
             for(int i = 0; i < hostData.Length; i++)
             {
                 if(GUI.Button(new Rect(Screen.width / 2, 65f + (30f * i), 300f, 30f), hostData[i].gameName + " #TEST-SERVER"))
                 {
                     Network.Connect (hostData[i]);
                 }
             }
         }
     }
 
 }