trailing space in polymer attributes causes exception in IE10

[frankiefu]

<polymer-element name="x-foo" noscript attributes="bar ">
  <template>
    {{bar}}
  </template>
</polymer-element>

<x-foo bar="hello"></x-foo>

output:

TypeError: Unable to get property 'hasAttribute' of undefined or null referenceTypeError: Unable to get property 'hasAttribute' of undefined or null reference
at parseDeclaration (http://172.31.55.70/polymer/polymer/src/instance/base.js:95:9)
at parseDeclarations (http://172.31.55.70/polymer/polymer/src/instance/base.js:88:9)
at prepareElement (http://172.31.55.70/polymer/polymer/src/instance/base.js:43:7)
at createdCallback (http://172.31.55.70/polymer/polymer/src/instance/base.js:25:9)
at created (http://172.31.55.70/polymer/CustomElements/src/CustomElements.js:264:7)
at upgrade (http://172.31.55.70/polymer/CustomElements/src/CustomElements.js:219:5)
at upgradeElement (http://172.31.55.70/polymer/CustomElements/src/CustomElements.js:321:7)
at upgrade (http://172.31.55.70/polymer/CustomElements/src/Observer.js:84:7)
at added (http://172.31.55.70/polymer/CustomElements/src/Observer.js:56:3)
at Anonymous function (http://172.31.55.70/polymer/CustomElements/src/Observer.js:66:5)

Debugging shows that in declaration/attributes.js::publishAttributes(), an empty string is added to the publish object, e.g. {bar: null, "": null}. Somehow this seems to be fatal in IE10.

In publishAttributes(), it should add to publish only if the name is not emtpy.