title: PatchValue or setValue with formGroup more formArray and formGroup
body: <p>I have the second forms. I need to fill in the fields with the date coming from the bank, a json file. In the <code>populateFields</code> method I get a parameter with the data that will be filled. But, it fills only the values ​​of <code>itens</code>, description that is inside the array, it does not execute. </p>
  
  <p>Error: </p>
  
  <blockquote>
    <p>ERROR Error: Uncaught (in promise): TypeError: _this.form.controls.itens.value [i] .description.patchValue is not a function</p>
  </blockquote>
  
  <p>I tried to use the following expression:</p>
  
  <pre><code>this.form.controls.itens.value[i].description.patchValue(item.description); 
  </code></pre>
  
  <p>However, I get the error mentioned above.</p>
  
  <pre><code> generateFormGroup(): void {
          this.form = this._formBuilder.group({
            id: [null],
            alias: ['Relatório de Despesa', [Validators.required, Validators.maxLength(50)]],
            job: [null, [Validators.required]],
            customer: [{ value: null, disabled: true }, [Validators.required]],
            contact: [{ value: null, disabled: true }, [Validators.required]],
            currency: [{ value: 1, disabled: true }, [Validators.required]],
            exchangeRate: [{ value: null, disabled: true }],
            advanceValue: ['0'],
            itens: this._formBuilder.array([this.createItem()]),
          });
        }
  
        createItem(): any {
          return this._formBuilder.group({
            id: [null],
            product: [null, [Validators.required]],
            productIcon: [null],
            description: this._formBuilder.group({
              descriptionProduct: [null],
              origin: [null],
              km: [null],
              destination: [null],
              rental: [null],
              days: [null],
              reason: [null],
              taglist: [null]
            }),
            date: [this.today, [Validators.required]],
            value: [0, [Validators.required, Validators.min(0.01)]],
            currency: [{ value: 1, disabled: true }, [Validators.required]],
            currencyAlias: [this.currency],
            receipt: [null],
            isLoading: [false],
            receiptId: [null],
            receiptExtension: [null],
          });
        }
  
      populateFields(data: any): void { 
   data.itens.forEach((item, i) =&gt; {
   this.form.controls.itens.value [i] .description.patchValue (item.description) // error
            }   
              this.itens = data.itens;
              this.form.controls.itens.patchValue(data.itens);
  
        }
  </code></pre>