Radio button value does not work correctly with falsy values

[tofesath]

Bug, feature request, or proposal:

Radio button component of value does not work correctly, when contains some falsy values: 0, '', false. When you click some falsy value in row. Second option get focus, but is not checked.

What is the expected behavior?

Option should be checked when contains some falsy value.

What is the current behavior?

When I clicked some falsy value in row. Second option get focus, but is not checked.

What are the steps to reproduce?

editor: https://stackblitz.com/edit/angular-h3gkag
app url: https://angular-h3gkag.stackblitz.io

What is the use-case or motivation for changing an existing behavior?

It is normal use case add a value some falsy value.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Tested on Angular 5.2.3/Material 5.2.1, all browsers

Is there anything else we should know?

I think, that problem is in the file below. Check loose equality evalute how false.
https://github.com/angular/material2/blob/master/src/lib/radio/radio.ts#L581

and this condition in same file is never execution.
https://github.com/angular/material2/blob/master/src/lib/radio/radio.ts#L588

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