title: vue comment not appended
body: <p>My Vue Code is not working until I refresh the page. The reply of the comment goes to database successfully, but is not showing in browser until I refresh the page or I add a comment then refresh then add reply.</p>
  
  <p>Comments.vue</p>
  
  <p>My Methods</p>
  
  <pre><code>appendReply(comment,reply){
      _.find(this.comments, { id: comment.id }).children.push(reply)
  },
  </code></pre>
  
  <p>Mounted </p>
  
  <pre><code>bus.$on('comment:replied', ({ comment, reply }) =&gt; {
      this.appendReply(comment, reply)
      this.scrollToComment(reply)
  })
  </code></pre>
  
  <p>I'm getting this error in console</p>
  
  <blockquote>
    <p>[Vue warn]: Error in event handler for "comment:replied": "TypeError:
    Cannot read property 'push' of undefined"</p>
  </blockquote>