❔ So i'm learning how to transition from one level to another and I got this error.

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

public class Score : MonoBehaviour
{
    public Text scoreDisplay;
    public int threeStars = 3;
    public int twoStars = 5;
    public Animator scoreAnimator;
    public int nextLevel = 0;

    public void EndLevel()
    {
        Cannon cannon = FindObjectOfType<Cannon>();

        if (cannon)
        {
            int numProjectiles = cannon.numProjectiles;

            if (numProjectiles < threeStars)
            {
                print("Three Stars!");
                scoreDisplay.text = "Three Stars!";
                scoreAnimator.SetInteger("Stars", 3);
            }
            else if (numProjectiles < twoStars)
            {
                print("Two Stars!");
                scoreDisplay.text = "Two Stars!";
                scoreAnimator.SetInteger("Stars", 2);
            }
            else 
            {
                print("One Star!");
                scoreDisplay.text = "One Star! Try Again!";
                scoreAnimator.SetInteger("Stars", 1);
            }
            NextLevel();
            
        }

        void NextLevel()
        {
            SceneManager.LoadScene(nextLevel);
        }

    }
}

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

public class Score : MonoBehaviour
{
    public Text scoreDisplay;
    public int threeStars = 3;
    public int twoStars = 5;
    public Animator scoreAnimator;
    public int nextLevel = 0;

    public void EndLevel()
    {
        Cannon cannon = FindObjectOfType<Cannon>();

        if (cannon)
        {
            int numProjectiles = cannon.numProjectiles;

            if (numProjectiles < threeStars)
            {
                print("Three Stars!");
                scoreDisplay.text = "Three Stars!";
                scoreAnimator.SetInteger("Stars", 3);
            }
            else if (numProjectiles < twoStars)
            {
                print("Two Stars!");
                scoreDisplay.text = "Two Stars!";
                scoreAnimator.SetInteger("Stars", 2);
            }
            else 
            {
                print("One Star!");
                scoreDisplay.text = "One Star! Try Again!";
                scoreAnimator.SetInteger("Stars", 1);
            }
            NextLevel();
            
        }

        void NextLevel()
        {
            SceneManager.LoadScene(nextLevel);
        }

    }
}