doveadm sis deduplicate: Error handling fix if open() fails. Found by Coverity.
doveadm sis deduplicate: Error handling fix if open() fails.
Found by Coverity.

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