message: tidy up UDE handler
diff: @@ -22,7 +22,7 @@ let isDialogOpen = false;
  const onAction = function(payload) {
  if (payload.action === 'unknown_device_error' && !isDialogOpen) {
  - var UnknownDeviceDialog = sdk.getComponent("dialogs.UnknownDeviceDialog");
  + const UnknownDeviceDialog = sdk.getComponent('dialogs.UnknownDeviceDialog');
  isDialogOpen = true;
  Modal.createDialog(UnknownDeviceDialog, {
  devices: payload.err.devices,
  @@ -33,9 +33,9 @@ const onAction = function(payload) {
  // https://github.com/vector-im/riot-web/issues/3148
  console.log('UnknownDeviceDialog closed with '+r);
  },
  - }, "mx_Dialog_unknownDevice");
  - }
  + }, 'mx_Dialog_unknownDevice');
  }
  +};
  let ref = null;
  