message: Fix the bug: knockout reset the value in dropdown, if there is no such value in options:
diff: @@ -51,10 +51,13 @@ export class QuestionImplementor extends QuestionImplementorBase {
  protected updateQuestion() {
  this.updateKoDummy();
  }
  + private isValueChangedPerforming = false;
  protected onValueChanged() {
  var val = this.question.value;
  if (Helpers.isTwoValueEquals(val, this.koValue())) return;
  + this.isValueChangedPerforming = true;
  this.setkoValue(val);
  + this.isValueChangedPerforming = false;
  }
  protected onCommentChanged() {
  var val = this.question.comment;
  @@ -81,6 +84,7 @@ export class QuestionImplementor extends QuestionImplementorBase {
  this.koValue(newValue);
  }
  protected updateValue(newValue: any) {
  + if (this.isValueChangedPerforming) return;
  if (!Helpers.isTwoValueEquals(this.question.value, newValue)) {
  this.question.value = newValue;
  }
  