Add null check before copying name fields

Bail if either name value delta is null. This can happen because
external read only raw contacts may not have a StructuredName, such
as the ones created by the Signal app.
User facing consequence is the name isn't auto copied for them, but
without a StructuredName type declared by the read only raw contact
there isn't a reliable way to even get something to copy.

Test: Verified editing a Signal raw contact doesn't crash the app
and the editor loads with the same behavior as if a new contact was
being created.

Bug: 33622717
Change-Id: I87b513ca9f188750f0d5e4e5f5392e419565cf4e