Firebase Auth Login and Signup app crashes when button clicked

Question

I am building a simple firebase login and signup application. It contains three activities, SignUp, LogIn and Profile activities. I have integrated Firebase, but the app crashes with an error when I click on either LogIn or SignUp button. I have gone through the entire forum looking for possible fix but couldn't find a right solution to fix my problem. How can I fix this problem?

Sharing my Login activity as reference code:-

    public class LoginActivity extends AppCompatActivity {
    //view binding
    private ActivityLoginBinding binding;

    //firebase auth
    private FirebaseAuth firebaseAuth;

    //progress dialog
    private ProgressDialog progressDialog;

    //actionBar
    private ActionBar actionBar;

    private String email="", password="";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityLoginBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        //Configure action bar, title
        actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.setTitle("LogIn");
        }

        //Configure progress dialog
        progressDialog = new ProgressDialog(this);
        progressDialog.setTitle("Please wait");
        progressDialog.setMessage("Logging In");
        progressDialog.setCanceledOnTouchOutside(false);

        //Initialise firebase auth
        firebaseAuth = FirebaseAuth.getInstance();
        checkUser();


        //if have account, SignUp
        binding.haveAccountTv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(LoginActivity.this ,SignUpActivity.class));
                finish();
            }
        });

        binding.loginBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                validateData();
            }
        });
    }

    private void checkUser() {
        //check if user is already logged in
        //get current user
        //if already logged in, then open profile activity
        FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
        if(firebaseUser != null){
            //user is already logged in
            startActivity(new Intent(this, ProfileActivity.class));
            finish();
        }

    }

    //Method 1 : Validate User Data
    private void validateData() {
        String email = binding.emailEt.getText().toString().trim();
        String password = binding.passwordEt.getText().toString().trim();

        if(TextUtils.isEmpty(email)){
            binding.emailEt.setError("This field cannot be empty");
        }
        else if(!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
            binding.emailEt.setError("Invalid Email format");
        }
        else if(TextUtils.isEmpty(password)){
            binding.passwordEt.setError("This field cannot be empty");
        }
        else if(password.length() < 6){
            binding.passwordEt.setError("Password must be atleast 6 characters long");
        }
        else {
            //data is valid. Now continue to firebase LogIn.
            firebaseLogIn();
        }
    }

    //Method 2 : Firebase Log in
    private void firebaseLogIn(){
        //show progress
        progressDialog.show();

        firebaseAuth.signInWithEmailAndPassword(email,password).addOnSuccessListener(new OnSuccessListener<AuthResult>() {
            @Override
            public void onSuccess(AuthResult authResult) {
                //login success
                progressDialog.dismiss();
                //get user info
                FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
                String email = null;
                if (firebaseUser != null) {
                    email = firebaseUser.getEmail();
                }
                Toast.makeText(LoginActivity.this, "LoggedIn\n"+email, Toast.LENGTH_SHORT).show();
                //open profile activity
                startActivity(new Intent(LoginActivity.this, ProfileActivity.class));
                finish();
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                //login failed. get and show error message
                progressDialog.dismiss();
                Toast.makeText(LoginActivity.this, ""+e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });

    }
}

Also sharing the logcat below:-

--------- beginning of crash
2022-01-27 09:48:19.063 4915-4915/com.jaswikventures.firebaseloginsignup E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.jaswikventures.firebaseloginsignup, PID: 4915
    java.lang.IllegalArgumentException: Given String is empty or null
        at com.google.android.gms.common.internal.Preconditions.checkNotEmpty(com.google.android.gms:play-services-basement@@18.0.0:2)
        at com.google.firebase.auth.FirebaseAuth.signInWithEmailAndPassword(com.google.firebase:firebase-auth@@21.0.1:1)
        at com.jaswikventures.firebaseloginsignup.LoginActivity.firebaseLogIn(LoginActivity.java:118)
        at com.jaswikventures.firebaseloginsignup.LoginActivity.validateData(LoginActivity.java:109)
        at com.jaswikventures.firebaseloginsignup.LoginActivity.access$000(LoginActivity.java:22)
        at com.jaswikventures.firebaseloginsignup.LoginActivity$2.onClick(LoginActivity.java:72)
        at android.view.View.performClick(View.java:7448)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1131)
        at android.view.View.performClickInternal(View.java:7425)
        at android.view.View.access$3600(View.java:810)
        at android.view.View$PerformClick.run(View.java:28305)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
2022-01-27 09:48:19.065 530-3813/? W/ActivityTaskManager:   Force finishing activity com.jaswikventures.firebaseloginsignup/.LoginActivity

I thought covering below code with if statement would solve the problem but it didn't work.

String email = null;
if (firebaseUser != null) {
    email = firebaseUser.getEmail();
}