尝试将readyCallback与vuefire一起使用时，Firebase绑定源无效

import Vue from 'vue';
import VueFire from 'vuefire';
import firebase from 'firebase/app';
import 'firebase/database';

Vue.use(VueFire);

const firebaseConfig = {
  // Your Firebase config here
};

firebase.initializeApp(firebaseConfig);

new Vue({
  el: '#app',
  data: {
    items: []
  },
  created() {
    this.$bindAsArray('items', firebase.database().ref('items'), {
      readyCallback: () => {
        console.log('Data is ready!');
      }
    });
  }
});

const firebaseConfig = {
  apiKey: "your-api-key",
  authDomain: "your-auth-domain",
  databaseURL: "your-database-url",
  projectId: "your-project-id",
  storageBucket: "your-storage-bucket",
  messagingSenderId: "your-messaging-sender-id",
  appId: "your-app-id"
};

npm update vuefire firebase

created() {
  this.$bindAsArray('items', firebase.database().ref('items')).then(() => {
    this.$nextTick(() => {
      console.log('Data is ready!');
    });
  });
}