imap-zlib: Fixed crash if imap_zlib_compress_level setting wasn't set.
imap-zlib: Fixed crash if imap_zlib_compress_level setting wasn't set.

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