null reference help. i fundamentally dont understand.

when trying to build my menu screen, i keep recieving null reference exceptions. it occurs when i press one of the two buttons on my screen. the two buttons controller whether im trying to register or log in. here is my code: i get the errors at mainmenu line 62 and login line 37

Main Menu Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class MainMenu : MonoBehaviour {
 
     private Register register;
     private LogIn login;
     public Button openRegister, openLog, registerButton, LoginButton;
     public InputField email, password, newEmail, newPassword, confirm;
     public GameObject game;
     
     private string em, pass, newEm, newPass, conf;
 
     //leave the error texts and stuff for now
 
 
 
     // Use this for initialization
     void Start () {
         Register register = game.GetComponent<Register>();
         LogIn login = game.GetComponent<LogIn>();
 
         //set the buttons from the log and register scripts
         login.initButtons();
         register.initButtons();
 
         
     }
     
     // Update is called once per frame
     void Update () {
         em = email.text;
         pass = password.text;
         newEm = newEmail.text;
         newPass = password.text;
         conf = confirm.text;
 
         openLog.onClick.AddListener(openLogClick);
         openRegister.onClick.AddListener(openRegisterClick);
     }
     
     void setStrings()
     {
         em = email.text;
         pass = password.text;
         newEm = newEmail.text;
         newPass = password.text;
         conf = confirm.text;
     }
 
     void openLogClick()
     {
         login = new LogIn();
         login.logIn(em, pass);
     }
 
     void openRegisterClick()
     {
 
         register.registerUser(newEm, newPass, conf);
     }
 }
 

Login Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using Firebase.Auth;
 using UnityEngine.SceneManagement;
 
 
 public class LogIn : MonoBehaviour {
 
     public InputField emailIn, passwordIn;
     public Button signInButton, openLogIn;
     public Text emailErrorText, passwordErrorText, successText;
     public GameObject eI, pI, sIButton, oLButton;
 
     private string emailString, passwordString;
     private FirebaseAuth auth;
     private bool userWantsLog = false , isButton = false;
 
     private Register checkUser;
     private Users user;
 
     private void Start()
     {
         emailErrorText.text = "";
         passwordErrorText.text = "";
         Register checkUser = GetComponent<Register>();
         Users user = GetComponent<Users>();
         initButtons();
 
         auth = FirebaseAuth.DefaultInstance;
 
     }
 
     public void logIn(string email, string password)
     {
         if(checkUser.UserChecker(email, password))
         {
             SceneManager.LoadScene(1);
         }
     }
 
     public void setAcctive()
     {
         eI.SetActive(true);
         pI.SetActive(true);
         sIButton.SetActive(true);
         oLButton.SetActive(false);
     }
 
     public void initButtons()
     {
         eI.SetActive(false);
         pI.SetActive(false);
         sIButton.SetActive(false);
         oLButton.SetActive(true);
 
     }
 
     void getStrings()
     {
         emailString = emailIn.text;
         passwordString = passwordIn.text;
     }
 
     void clickEvent()
     {
         isButton = true;
     }
     
     void openLogClick()
     {
         userWantsLog = true;
     }
 
     void log(string email, string password) {
 
         auth.SignInWithEmailAndPasswordAsync(email, password).ContinueWith(task => {
             if (task.IsCanceled)
             {
                 Debug.LogError("SignInWithEmailAndPasswordAsync was canceled.");
                 return;
             }
             if (task.IsFaulted)
             {
                 Debug.LogError("SignInWithEmailAndPasswordAsync encountered an error: " + task.Exception);
                 return;
             }
 
             Firebase.Auth.FirebaseUser newUser = task.Result;
             Debug.LogFormat("User signed in successfully: {0} ({1})",
                 newUser.DisplayName, newUser.UserId);
         });
     }
 }
 

Register Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 using Firebase.Unity.Editor;
 using UnityEngine.UI;
 using Firebase.Auth;
 using System.Linq;
 using UnityEngine.SceneManagement;
 
 public class Register : MonoBehaviour
 {
 
     public InputField Password, Email, Confirm;
     public Text success, errorText;
     public Button registerButton, openRegister;
     public GameObject nEM, nP, nCP, SU, registerObject;
 
     private Scene scene;
     private string email, password, conf;
     private bool successToken = false;
     private bool isRegister;
     private int userCount;
 
     private Users user;
     private FirebaseAuth auth;
     private SceneChanger change;
     private Users[] userArray;
     Scene currentScene;
 
     // Use this for initialization
     void Start()
 
     {
         isRegister = false;
         
         change = GetComponent<SceneChanger>();
         currentScene = SceneManager.GetActiveScene();
 
         userCount = 0;
         
         userArray = new Users[100];
        
         auth = FirebaseAuth.DefaultInstance;
         
         success.text = "";
         errorText.text = "";
     }
 
     public void registerUser(string email, string password, string confirm)
     {
         this.email = email;
         this.password = password;
         conf = confirm;
 
 
         //check whether the password meets criteria and whether they match
         checkPass();
         checkConfirm();
 
         if(checkPass() && checkConfirm())
         {
             if (UserChecker(this.email, this.password))
             {
                 addUser();
             }
         }
     }
 
     void setActive()
     {
         nEM.SetActive(true);
         nP.SetActive(true);
         nCP.SetActive(true);
         SU.SetActive(true);
         
     }
 
     public void initButtons()
     {
         nEM.SetActive(false);
         nP.SetActive(false);
         nCP.SetActive(false);
         SU.SetActive(false);
         registerObject.SetActive(true);
     }
 
     bool checkConfirm()
     {
         if (conf == password)
             return true;
         else
             return false;
     }
 
     bool checkPass()
     {
         if (password.Length >= 6 && password.Any(char.IsUpper) && password.Any(char.IsDigit)){
             return true;
         }
 
         else return false;
     }
 
     bool registerSuccessToken()
     {
         if (checkConfirm() && checkPass())
             return true;
         return false;
     }
     
     void signUp(string email, string password)
     {
 
         auth.CreateUserWithEmailAndPasswordAsync(email, password).ContinueWith(task => {
             if (task.IsCanceled)
             {
                 Debug.LogError("CreateUserWithEmailAndPasswordAsync was canceled.");
                 return;
             }
             if (task.IsFaulted)
             {
                 Debug.LogError("CreateUserWithEmailAndPasswordAsync encountered an error: " + task.Exception);
                 return;
             }
 
             // Firebase user has been created.
             Firebase.Auth.FirebaseUser newUser = task.Result;
             successToken = true;
             Debug.LogFormat("Firebase user created successfully: {0} ({1})",
                 newUser.DisplayName, newUser.UserId);
         });
         
     }
 
     void addUser()
     {
         user = new Users(email, password);
         userArray[userCount] = user;
         userCount++;
 
         Debug.Log(user.retEmail());
         Debug.Log("if there arent");
     }
 
 
     void registerB()
     {
         isRegister = true;
         nEM.SetActive(true);
         nP.SetActive(true);
         nCP.SetActive(true);
         SU.SetActive(true);
         registerObject.SetActive(false);
     }
     
     void singUpClicked()
     {
         Debug.Log("enters if. creating user");
         signUp(email, password);
         isRegister = false;
         setActive();
         registerObject.SetActive(true);
 
         addUser();
     }
     
     public bool UserChecker(string em, string pass)
     {
         //string emailHold, passHold;
         if (userArray.Length == 0)
         {
             errorText.text = "no users exist";
             return true;
         }
 
         else
         {
             for (int i = 0; i < userArray.Length; i++)
             {
                 Debug.Log(userArray[i].retEmail());
                 Debug.Log(userArray[i].retPass());
                 if (userArray[i].retEmail() == em && userArray[i].retPass() == pass)
                     return true;
             }
             return false;
         }
     }
 }

someone please help. i do not fundamentally get how to reference the other scripts.