istream-attachment-extractor: Fixed handling attachment as the message body without MIME. Don't crash at the end after parsing the base64 data.
istream-attachment-extractor: Fixed handling attachment as the message body without MIME.
Don't crash at the end after parsing the base64 data.

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