**EMPTY** is a SHOUTcast DNAS 2.x thing so it's more something that the DNAS needs to better support / implement.
luckily, as long as you're using a current DNAS 2.4x then you can if needed add blockemptyuseragent=1 in the config file and do a DNAS config reload via the DNAS server admin page (which saves having to restart the whole DNAS). i believe you can use the Centova raw config editor for editing the DNAS config file.
as for it adding **EMPTY** to the blocked user agent list, that's a DNAS bug and would need to be fixed.