<tr
*ngIf="existChildBedInRoom"
class="form-group"
[ngClass]="{'has-error': countOfChildBedInput.invalid && countOfChildBedInput.touched}">
</tr>
<tr *ngIf="existChildBedInRoom">
<td><label class="control-label" for="countOfChildBedInput">Count bed</label></td>
<td>
  <input
    type="number"
    name="countOfChildBedInput"
    id="countOfChildBedInput"
    placeholder="Enter number"
    class="form-control"
    required
    ngModel
    #countOfChildBedInput="ngModel"
  >
</td>
</tr>
<tr
*ngIf="countOfChildBedInput.invalid && countOfChildBedInput.touched"
class="text-center form-help-text"
><td colspan="3" style="background: #c40000; color: white">Not emty!</td>
</tr>

export class RoomInformationCardComponent implements OnInit {
  existChildBedInRoom: boolean;
  @ViewChild('childBedInRoom') childBedInRoom: ElementRef;

  constructor() { }

  ngOnInit() {
    this.existChildBedInRoom = false;
  }

}

ERROR TypeError: Cannot read property 'invalid' of undefined
at Object.eval [as updateDirectives] (RoomInformationCardComponent.html:92)
at Object.debugUpdateDirectives [as updateDirectives] (core.es5.js:13067)
at checkAndUpdateView (core.es5.js:12251)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)