message: ExpressionQuestion, fix a bug in vue:
diff: <template>
  - <div>:class="question.cssClasses.text">{{question.displayValue}}</div>
  + <div :class="question.cssClasses.text">{{question.displayValue}}</div>
  </template>
  <script lang="ts">
  @Component
  export default class Expression extends Question<QuestionExpressionModel> {
  - change(event) {
  - this.question.value = event.target.value;
  - }
  }
  Vue.component("survey-expression", Expression)
  </script>
  