According to the newest spec as of 7 August, 2018: https://www.w3.org/TR/webauthn/#conforming-authenticators-u2f. UserHandle can now be null.
Created attachment 354776 [details] Patch
Comment on attachment 354776 [details] Patch Thanks Alex for r+ this patch.
Comment on attachment 354776 [details] Patch Clearing flags on attachment: 354776 Committed r238238: <https://trac.webkit.org/changeset/238238>
All reviewed patches have been landed. Closing bug.
<rdar://problem/46103418>