FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call Firebase App.initializeApp() (app/no-app)

Question

I got this problem when I try to setup firebase whit next.js. I don't know what's going on.

firebase.js file

import firebase from 'firebase';
import 'firebase/auth';
import 'firebase/functions';
import 'firebase/firestore';

if (!firebase.apps.length) {
  firebase.initializeApp({
    apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
    authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
    projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID
  });
}
export default firebase;

I also create a .env.local and I added environment variables.

NEXT_PUBLIC_FIREBASE_API_KEY=xxxxxxxxxxxxxx
NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN=xxxxxxxxxxxxxxxxxxxxxxxxxxx
NEXT_PUBLIC_FIREBASE_PROJECT_ID=xxxxxxxxxxxxxxxxxxxxxxxxxxx