message: added gurad for case with `question == null`
diff: @@ -36,6 +36,7 @@ export class SurveyQuestion extends React.Component<any, any> {
  state.error++;
  this.setState(state);
  };
  + if (!this.question) return;
  this.question.titleChangedCallback = () => {
  var state = this.getState();
  state.error++;
  