lib-storage: Fixed STATUS_FIRST_UNSEEN_SEQ lookup with private flags index.
lib-storage: Fixed STATUS_FIRST_UNSEEN_SEQ lookup with private flags index.

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