Support Null device account

- Fully support when there are existing null contacts
- If there are no null contacts user can not create new ones

Bug:133778029
Test: Manually tested that when there is a Google account, null account
is shown in the drawer and in editor create new contact account list
only when null contacts already exist.

Change-Id: I9041a866f2c4a9359fbb173cd9a9861ecc2e8d36