mod_roster_command: Fix subscription when the "user JID" is a bare domain. Do not attempt to update the roster when the user is bare domain (e.g. a component), since they don't have rosters and the attempt results in an error: $ prosodyctl mod_roster_command subscribe proxy.example.com contact@example.com xxxxxxxxxxFailed to execute command: Error: /usr/lib/prosody/core/rostermanager.lua:104: attempt to concatenate local 'username' (a nil value) stack traceback: /usr/lib/prosody/core/rostermanager.lua:104: in function 'load_roster' /usr/lib/prosody/core/rostermanager.lua:305: in function 'set_contact_pending_out' mod_roster_command.lua:44: in function 'subscribe'

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summary: 'Block remote servers via ad-hoc command'
...

Introduction
============

This module provides the *Edit Blacklist* ad-hoc command described in
[XEP-0133](http://xmpp.org/extensions/xep-0133.html#edit-blacklist) and
also performs the actual blocking of incoming and outgoing
server-to-server connections.

Using
=====

In your client, simply select the Edit Blacklist command from the list
of adhoc commands. E.g. in Pidgin, this is under *Accounts -\> (your
account)* in the menu.