nb-datepicker reactive form validation issue

[maihannijat]

Issue type

I'm submitting a ... (check one with "x")

• [ x] bug report
• feature request

Issue description

Current behavior:

Using Input with [nbDatepicker]="datePicker" and Reactive Form. The validation rule is not defined and there is no required keyword in the template but leaving the input field empty makes the form invalid. The form is valid if date is entered.

Expected behavior:

A form with input empty (null) should be valid if it's not required and there is no validation rule.

Steps to reproduce:

1- Create Reactive Form with input having date picker.

Related code:

<nb-card>
	<nb-card-header>Fill the form</nb-card-header>
	<nb-card-body>

		<form [formGroup]="form" (ngSubmit)="submit()" aria-labelledby="title">

			<input nbInput
                   fullWidth
                   [nbDatepicker]="datePicker"
                   placeholder="Date"
                   formControlName="dateCtrl">
      <nb-datepicker #datePicker></nb-datepicker>

        <button nbButton
                    [disabled]="!form.valid">
              Submit
        </button>
    </form>
  </nb-card-body>
</nb-card>

export class AppComponent implements OnInit  {

  form;

  constructor(private fb: FormBuilder) {

  }

  submit() {
    alert('Valid Form');
  }

  ngOnInit() {
      this.form = this.fb.group({
      dateCtrl: [''],
    });
  }
}

StackBlitz StackBlitz Project

Note: Leave the field empty and click submit which is not clickable and then enter 2019-05-05 and you will see alert.