If extension record was tried to be updated for uid=0, log an error instead of crashing. Also log error if uid >= next_uid.
If extension record was tried to be updated for uid=0, log an error instead
of crashing. Also log error if uid >= next_uid.

--HG--
branch : HEAD

jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jkerihuel/dovecot