Angular 6被动窗体自定义验证器从默认数据中获取错误

我有一个自定义验证器,它检查每个FormArray中的所有数据,以验证数据的重复。目前,它还在用自身验证初始数据,这会引发一个错误。

当添加新数据时,它工作正常,并且与现有数据具有相同的值。

for (let assign of this.additionalAssign) {
      const fg = new FormGroup({
        "payRate": new FormControl(assign.jobRate, Validators.required),
        "position": new FormControl(assign.position, Validators.required),
        "location": new FormControl(assign.location, Validators.required),
        "department": new FormControl(assign.department, Validators.required)
      }); 
      fg.validator = this.jobDataValidator.bind(this);
      this.addPay.push(fg);
    }

jobDataValidator(control: FormControl): {[s: string]: boolean} {
        let value = this.getJobLocDeptValidity(control);
        if(value.length > 0){
          return {'sameJobData': true};
        }
        return null;
      }

getJobLocDeptValidity(control: FormControl):any[] {
            let additionalAssignments = this.additionalAssignmentsForm.value.payArray;
            let test = additionalAssignments.filter(item =>  !!control.value.position && item.position ===              !control.value.location && item.location === control.value.location);
            return test;
          }

截图:

Stackblitz网址: https://stackblitz.com/edit/angular-custom-validator-defaultdata