message: use namespace string from strophe
diff: @@ -1422,7 +1422,7 @@ jsxc.muc = {
  msg: $.t('message_not_send_not-acceptable')
  });
  } else if ($(message).find('service-unavailable').length > 0) {
  - if ($(message).find("[xmlns='http://jabber.org/protocol/chatstates']").length === 0) {
  + if ($(message).find('[xmlns="' + Strophe.NS.CHATSTATES + '"]').length === 0) {
  jsxc.gui.window.postMessage({
  bid: room,
  direction: jsxc.Message.SYS,
  