m_ison: Do not report unregistered connections
Created by: thegrumble
Prior to this, m_ison would report a nick as being online if a client that was not yet registered had chosen this nickname on the same server. This change adds a check to make sure the
struct Client has a
struct User associated with it, i.e. registration has occurred.
A bit of local testing with a single ircd says it works as intended, but I haven't been able to test it with multiple servers yet.