离子相机:没有值存取器的形式控制与名称

我用的是 cordova插件相机 离子型应用程序中的插件。我成功地让相机拍了一张照片,并在出现以下错误后显示出来:

No value accessor for form control with name 'photo'

注册.html

<img *ngIf="register_form.controls.photo.value != ''" formControlName="photo" [src]="domSanitizer.bypassSecurityTrustUrl(register_form.controls.photo.value)" />

register.ts文件

ionViewWillLoad() {
  this.register_form = this.formBuilder.group({
    ...
    photo: new FormControl('', Validators.required)
  });
}
...
onTakePicture(){
  ...
  this.camera.getPicture(options).then((imageData) => {
        const image: FormControl = (<any>this.register_form).controls.photo;
        image.setValue('data:image/jpeg;base64,' + imageData);
    }, (err) => {
  });
}

怎么了?