属性“ _touched”是私有的，只能在类“ AbstractControl”中访问。

生产构建错误

嗨，我在Angular Project中使用ReactiveForms，当我尝试ng build --prod时，出现以下错误

ng-details/billing-details.component.html (40,6): Property '_touched' is private
 and only accessible within class 'AbstractControl'.

以下是我的代码，我不知道哪里出错了？

  paymentForm = new FormGroup({
    companyName: new FormControl('', Validators.minLength(3)),
    companyAddress: new FormControl('', Validators.minLength(3)),
    gstNumber: new FormControl('', Validators.minLength(3)),
    country: new FormControl('', Validators.minLength(3)),
    cardNumber: new FormControl('', Validators.pattern('[0-9]{12}')),
    cardName: new FormControl('')    
  });

HTML

<div class="common-error" *ngIf="paymentForm.controls.country._touched && !paymentForm.controls.country.valid"> Please enter Company Name. (Min 3 char)</div>