Don't allow FETCH BODY[HEADER.FIELDS ()], ie. empty list.
Don't allow FETCH BODY[HEADER.FIELDS ()], ie. empty list.

--HG--
branch : HEAD

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