This one actually fails. Quick patch to make it pass:

```diff
diff --git a/static/js/chat/models.js b/static/js/chat/models.js
index 29425e7..556334b 100644
--- a/static/js/chat/models.js
+++ b/static/js/chat/models.js
@@ -264,6 +264,9 @@
    *
    */
   app.models.FileTransfer = Backbone.Model.extend({
+    defaults: {
+      progress: 0
+    },
 
     /**
      * Filetransfer model constructor.
```