[0.8] Data-binding icon to computed value causes exception

[justinfagnani]

I'm trying to use core-icon like this:

<core-icon icon="[[getIcon(data)]]"></core-icon>

getIcon(data) {
  return "icons:folder";
}

Which causes this exception:

Uncaught TypeError: Cannot read property 'applyIcon' of undefinedPolymer.updateIcon @ core-icon.html:174

Binding to a property works, so something in core could be partially to blame, but core-icon should probably be resilient to bad icon values.