[0.5.5] Event fire error on safari #1362

[Error] SyntaxError: DOM Exception 12: An invalid or illegal string was specified.
    dispatchOriginalEvent (webcomponents.js, line 964)
    dispatchEvent ([native code], line 0)
    dispatchEvent (webcomponents.js, line 1352)
    fire (polymer.min.js, line 13)
    sectionChanged ...

        sectionChanged: function(topic, json) {
                this.fire('section-change', json);
            },