Firebase Registration, Given String is empty or null

Question

Firebase Registration Error

My app shuts down when I click the registration button.

This is my Registration Button Code :

mRegistration.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final String email = mEmail.getText().toString();
                final String password = mPassword.getText().toString();
                mAuth.createUserWithEmailAndPassword(email, password).addOnCompleteListener(DriverLoginActivity.this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if(!task.isSuccessful()){
                            Toast.makeText(DriverLoginActivity.this, "sign up error", Toast.LENGTH_SHORT).show();
                        }else{
                            String user_id = mAuth.getCurrentUser().getUid();
                            DatabaseReference current_user_db = FirebaseDatabase.getInstance().getReference().child("Users").child("Drivers").child(user_id).child("name");
                            current_user_db.setValue(email);
                        }
                    }
                });
            }
        }); 

---

And this is the Error I get:

PID: 10284
java.lang.IllegalArgumentException: Given String is empty or null
    at com.google.android.gms.common.internal.zzbq.zzgi(Unknown Source)
    at com.google.firebase.auth.FirebaseAuth.createUserWithEmailAndPassword(Unknown Source)
    at in.co.shahilislam.parkspot.DriverLoginActivity$2.onClick(DriverLoginActivity.java:57)

Thanks.