"message": "SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'users_email_unique'

Hey so I have a login module that is suddenly giving me an error

"message": "SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'users_email_unique' (SQL: insert into `users` (`updated_at`, `created_at`) values (2018-10-11 13:17:54, 2018-10-11 13:17:54))",

the login code looks like

 //The createToken method is one of the methods Laravel Passport adds to the user model.
    public function login(Request $request) {

        if(Auth::attempt(['email' => $request->get('email'), 'password' => $request->get('password')])) {
            $status = 200;
            $response = [
                'user' => Auth::user(),
                'token' => Auth::user()->create(['bigStore'])->accessToken,
            ];
        return response()->json($response, $status);
        }else {
            $status = 401;
            $response = ['error' => 'Unauthorised'];
            return response()->json($response, $status);
        }

    }

and the front end is

handleSubmit(e) {
                e.preventDefault();
                if (this.password.length > 0) {
                    let email = this.email;
                    let password = this.password;

                    axios.post('api/login', {email, password}).then(response => {
                        let user = response.data.user;
                        let is_admin = user.is_admin;

                        localStorage.setItem('bigStore.user', JSON.stringify(user));
                        localStorage.setItem('bigStore.jwt', response.data.token);

                        if (localStorage.getItem('bigStore.jwt') != null) {
                            this.$emit('loggedIn');
                            if (this.$route.params.nextUrl != null) {
                                this.$router.push(this.$route.params.nextUrl)
                            } else {
                                this.$router.push((is_admin === 1 ? 'admin' : 'dashboard'))
                            }
                        }
                    });
                }
            }