why is candidate stats nullable instead of an empty string?

[fippo]

i'm currently adding an alias for chrome/webrtc's ip field on candidate statistics. However, one of the WPT failed because for prflx addresses the field is an empty string instead of null.

The test was added in https://github.com/web-platform-tests/wpt/pull/13922 and the spec change is in https://github.com/w3c/webrtc-stats/pull/381

Is there a specific reason for using a DOMString? instead of a DOMString which is empty? Firefox puts "redacted" there.

@youennf you might remember (and might want to check if this commit breaks anything for you or you can just simplify some code :soon:)

[henbos]

Let's change it to empty string.

[henbos]

What does the implementation do today?