Alguém pode me dizer o porquê de dar NullException?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class GAMEMANAGER : MonoBehaviour
{

public static GAMEMANAGER inst,instance;


public bool gameover=false;
public GameObject heroi;
public Transform pos;
public int ondeEstou;
public bool jogoComecou;
public int personagem;



enum character
{
    personagem = 0,
};


void Awake()
{
    if (inst == null)
    {
        inst = this;
        DontDestroyOnLoad(this.gameObject);
    }
    else
    {
        Destroy(gameObject);           
    }

    SceneManager.sceneLoaded += Carrega;

}

void Carrega(Scene cena, LoadSceneMode modo)
{

    pos = GameObject.Find("Corpo").GetComponent<Transform>();
   
}

void Start()
{
   
}
void Update()
{

    if (gameover == true)
    {
        GameOver();
    }
   
}


void GameOver()
{
    UIManager.instance.GameOverUI();
}


void StartGame()
{
    jogoComecou = true;
    UIManager.instance.StartUI();
}

}
NullReferenceException: Object reference not set to an instance of an object
GAMEMANAGER.GameOver () (at Assets/Scripts/GAMEMANAGER.cs:68)
GAMEMANAGER.Update () (at Assets/Scripts/GAMEMANAGER.cs:60)