Fix issue with radio defaults

A patched build of this branch is available here for testing: [Rivets 0.7.1-p1](https://rawgit.com/mikeric/0e549ef1ea0ad0b876b8/raw/ee72c887692a6f4b8bd5c9753ceda308029877d8/rivets-0.7.1-p1.bundled.min.js)

#422