lib-storage: Fixed assert-crash when trying to fetch a binary section for empty message.
lib-storage: Fixed assert-crash when trying to fetch a binary section for empty message.

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot