lib-index: Make sure a corrupted mail_cache_header_fields.size doesn't cause crashes.
lib-index: Make sure a corrupted mail_cache_header_fields.size doesn't cause crashes.

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