Cannot read property 'slice' of undefined on firebase update

[Illuday]

Hey! :)

I link my polymer to firebase with this :

<link rel="import" href="../../bower_components/polymer/polymer.html">
<link rel="import" href="../../bower_components/firebase-element/firebase-collection.html"> 

<dom-module id="list-activity">
  <template>
    <firebase-collection
      location="https://glaring-inferno-8584.firebaseio.com/activity"
      data="{{activity}}"></firebase-collection>
    <template is="dom-repeat" items="[[activity]]" as="a">
      <h4>[[a.id]]</h4>
      <span>Title: </span><span>[[a.title]]</span>
    </template>
  </template>
</dom-module>

<script>
  Polymer({
    is: "list-activity"    
  });
</script>

Everything works fine at first display. But when I update a entry of firebase it return in Console :

Uncaught TypeError: Cannot read property 'slice' of undefined     ____    polymer.html:1727

And nothing is update in my html template. However, when I add an entry in firebase, it add to my template without any errors.

[kevinpschaaf]

This sounds like a <firebase-collection> issue, we'll move this issue to that repo.

[tjsavage]

auto-moving this issue to GoogleWebComponents/firebase-element#27 and closing this one