title: Reactive form dynamic field validation not working for <Select>
body: <p>I have a reactive form that contains form array when the user clicks on a button, a  new form group is pushed to the form array. When the user submits the form I want to validate whether those dynamic fields are empty
  <code>room.errors?.required</code> is not executed. What I am doing wrong here? Other fields are working as I expected. This issue occurs only in the dynamic field.</p>
  
  <pre class="lang-js prettyprint-override"><code>    this.formBuilder.group({
        email: ["", [Validators.required, Validators.email]],
        description: ["", [Validators.required, Validators.maxLength(300)]],
        roomTypes: this.formBuilder.array([this.createRoomTypeFeild(),this.createRoomTypeFeild()
        ]),
      }); 
  </code></pre>
  
  <p>this method is used for creating dynamic form field when the user click on the button</p>
  
  <pre class="lang-js prettyprint-override"><code>    createRoomTypeFeild(): FormGroup {
          return this.formBuilder.group({
              id: [""],
              room: ["",Validators.required],
              price: ["",Validators.required]
          });
      }
  </code></pre>
  
  <p>this is simple getter I used to get the field to  the template</p>
  
  <pre class="lang-js prettyprint-override"><code>    get extraRoomTypes() {
          return this.hospitalForm.get("roomTypes") as FormArray;
      }
  </code></pre>
  
  <p>when the user clicks on a button this method executes</p>
  
  <pre class="lang-js prettyprint-override"><code>    addMoreFeilds(feildName: string) {
          let formArray: FormArray = this.hospitalForm.get(feildName) as FormArray;
          if (feildName === "roomTypes") formArray.push(this.createRoomTypeFeild());
      }
  </code></pre>
  
  <p>Template</p>
  
  <pre class="lang-html prettyprint-override"><code>    &lt;tr formArrayName="roomTypes" *ngFor="let roomType of extraRoomTypes.controls;let i = index"&gt;
          &lt;td&gt;
              &lt;div [formGroupName]="i" class="row"&gt;
                  &lt;div class="col-sm-6"&gt;
                      &lt;div class="form-group row"&gt;
  
                          &lt;label class="col-sm-2 col-form-label form-field"&gt;Room&lt;/label&gt;
                          &lt;div class="col-sm-9 table-input"&gt;
  
                              &lt;select formControlName="room" type="text" class="form-control"&gt;
                                  &lt;option [ngValue]="room.id" *ngFor="let room of filterdRoomTypes"&gt;{{room.roomType}}&lt;/option&gt;
                              &lt;/select&gt;
                              &lt;div *ngIf="isSubmitted &amp;&amp; hospitalForm.errors" class="error-msg"&gt;
                                  &lt;div *ngIf="room.errors?.required"&gt;
                                      Room is required
                                  &lt;/div&gt;
  
                              &lt;/div&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="col-sm-5"&gt;
                      &lt;div class="form-group row"&gt;
                          &lt;label class="col-sm-5 col-form-label pl-0 form-field"&gt;Price
  
                          &lt;/label&gt;
                          &lt;div class="col-sm-6"&gt;
                              &lt;input formControlName="pricePerNight" currencyMask [options]="{ prefix: '$ ', thousands: ',', decimal: '.',align:'left' }" type="text" class="form-control price"&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
  
              &lt;/div&gt;
          &lt;/td&gt;
      &lt;/tr&gt;
  
  </code></pre>