@Override
    protected List<Action> getActions(@Nonnull final SessionData data) {
        //Do nothing since there are no stages
        return null;
    }
Command that allows to retrieve the number of registered users

@author Guus der Kinderen, guus@goodbytes.nl
@see <a href="https://xmpp.org/extensions/xep-0133.html#get-registered-users-num">XEP-0133 Service Administration: Get Number of Registered Users</a>
xmppserver/src/main/java/org/jivesoftware/openfire/commands/admin/GetNumberRegisteredUsers.java