digest_md5_generate(): If username isn't given, give an error message instead of crashing. Mostly to avoid crashing with dovecotpw utility.
digest_md5_generate(): If username isn't given, give an error message
instead of crashing. Mostly to avoid crashing with dovecotpw utility.

--HG--
branch : HEAD

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