Don't assert-crash if first mail is expunged and we're doing a full sync.
Don't assert-crash if first mail is expunged and we're doing a full sync.

--HG--
branch : HEAD

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