Description

Paper radio button names that evaluate to false can be deselected without allow-empty-selection
This becomes significant when the name is bound to index in a template dom-repeat.

Expected outcome

It should be impossible to deselect the a radio button, even if it is the only one selected.

Actual outcome

It is possible to deselect radio buttons with name set to "0".

I think it's because the check below (in paper-radio-group.html) fails when this.selected = 0 or "0", which makes the code feel its fine to toggle the radio button.

   select: function(value) {
      \\ ...
      if (this.selected) {
       \\ ...
      }
      \\ ...

Live Demo

https://jsbin.com/pocisukaqe/edit?html,css,output
(also contains a hacky solution)

Steps to reproduce

1. Put a paper-radio-group with a few paper-radio-buttons on a page.
2. Set the name of the first paper radio buttons to "0", and the names of the others to any values.
3. Open the page in a web browser.
4. Press the first radio button. Press it again to see it is toggleable, without allow-empty-selection.
5. Press a different radio button. Press it again to see it is not toggleable.