title: Vue Firebase : currentUser is null
body: <p>I'm new in Vue and Firebase. I'm using Firebase query to retrieve some data from Firebase database based on the current user email. </p>
  
  <p><strong>This is working</strong> </p>
  
  <pre><code>source:firebase.database().ref('service').orderByChild('userEmail').equalTo('shakil@gmail.com')
  </code></pre>
  
  <p>So in this case I'm using <strong>firebase.auth().currentUser.email</strong> for using current user email</p>
  
  <p><strong>But this is not working</strong></p>
  
  <pre><code>source:firebase.database().ref('service').orderByChild('userEmail').equalTo(firebase.auth().currentUser.email)
  </code></pre>
  
  <p>It shows a error like this-> <strong>firebase___default.a.auth(...).currentUser is null</strong></p>
  
  <p><strong>And here is how Im using it into vuefire</strong></p>
  
  <pre><code>firebase: {
        services: {
          source: firebase.database().ref('service').orderByChild('userEmail').equalTo('marin@gmail.com'),
          readyCallback () {
            this.services.forEach(service =&gt; {
              firebase.storage()
                .ref(`service_images/${service.fileName}`)
                .getDownloadURL()
                .then(img =&gt; {
                  this.$set(this.serviceImages, service['.key'], img)
                })
            })
          }
      }
    },
  </code></pre>