In `wp.media.view.Attachment.render` tested parameter is missing an initialization.

[georgestephanis]

I'm still familiarizing myself with Media, so please feel free to close if this is silly.

On line ~116 in wp-includes/js/media/views/attachment.js we're testing:

`
if ( options.nonces ) {
`

but options.nonces isn't initialized above in the options defaults.

For clarity's sake, should we initialize it to false? (also, it keeps my IDE from getting cranky about it)

Patch attached.

Also -- options.percent isn't initialized either -- but as that seems to be conditionally initialized down below (only initialized if options.uploading is truthy), I didn't muck around with it in this patch.