Bro 0.6 and empty const values


I am working with Bro 0.6 at the moment, and have ran into an issue. In
the policy scripts, there are a number of const values that contain
machines that do not exist in our network, or machines that we are not
interested in (e.g., non_ASCII_hosts in login.bro). Is there a way to
specify that the const value is empty where it is declared? For
example, if our network does not have a ftp_server running, can we
assign a value to the line,

const ftp_servers = { ??? };

that will allow Bro to run, and avoid parsing errors?

I bring this up, because currently I am commenting some const values
out, and any reference to them in the scripts that depend on them. My
intuition tells me there must be another way.

One more thing. I was unable to subscribe to this mailing list via responds with a "use unknown" reply. If
anyone knows why this is, I would appreciate the information.