firebaseでundefinedを許容する

大体はこれと同じです。
https://zenn.dev/1023_310/articles/47911eadef1f1d#3.-firebaseに接続する
undefinedを許容したいとき、以下のように記載します。

src/libs/firebase.tsx

import { getApp, getApps, initializeApp } from 'firebase/app';

const firebaseConfig = {
  apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY || '',
  authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN || '',
  projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID || '',
  storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET || '',
  messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID || '',
  measurementId: process.env.NEXT_PUBLIC_FIREBASE_APP_ID || '',
  databaseURL: `https://${
    process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID || ''
  }.firebaseio.com`,
};

-  export const firebaseApp = !getApps().length
-    ? initializeApp(firebaseConfig)
-    : getApp();

+  const firebase = !getApps().length
+    ? initializeApp(firebaseConfig)
+    : getApp();
+  
+  initializeFirestore(firebase, {
+    ignoreUndefinedProperties: true,
+  });
+  
+  export const firebaseApp = firebase;