Fixed bug where passive didn't comm. when conf=0

Passive previously didn't advertise according to the following condition:
  if (conf < CONF_THRESHOLD && conf < lastConf)

This is incorrect when lastConf = 0 and conf = 0, since we still want to advertise when we cannot see the object. This is now fixed by using (conf < CONF_THRESHOLD && (conf == 0 || conf < lastConf))