I am trying to get a date value. Whenever the the checkbox is unchecked and the date picker is invisible I am getting the error that : 'Cannot read property 'NTLI' of undefined'. if the check box is checked and the date picker is visible everything works fine

<md-checkbox ng-model=user.NTLI layout=row ng-disabled=userForm.$invalid>

  NTLI

</md-checkbox>

<div ng-show=user.NTLI>

<fieldset class=standard>

    <legend>NTLI</legend>

    <md-input-container>

        <label>Efective date</label>

        <md-datepicker ng-model=user.efectiveDateNTLI></md-datepicker>

    </md-input-container>

</fieldset>

</div>

var efDate = '';

if ($scope.user.NTLI != undefined) 

{

    efDate = $scope.user.efectiveDateNTLI

}