Do not send NICK command when nick not changed

If we get a presence, that is not always a nick change. Don't bother the
IRC server with a command to change the nick if we're not changing it.

src/bridge/bridge.cpp

@@ -596,6 +596,9 @@ void Bridge::send_irc_nick_change(const Iid& iid, const std::string& new_nick, c
   if (!res_in_chan)
     return;
   IrcClient* irc = this->get_irc_client(iid.get_server());
+  if (new_nick == irc->get_own_nick())
+    return;
+
   irc->send_nick_command(new_nick);
 }