An exception is raised when the `onMachineTranslate` event is handled and Survey Creator is switched to read-only mode

[Andrew]

The following configuration may cause the exception in the Translation tab.

  const creator = new SurveyCreatorModel({ showTranslationTab: true });
  creator.onActiveTabChanging.add((sender, options) => {
    creator.readOnly = options.tabName !== "translation";
  });
  creator.onMachineTranslate.add((sender, options) => {});