title: Angular2 Form using setValue to reset value to null
body: <p><strong>Sorry for this question. This is to do with one of my child component which rejecting null, empty string while writing to form.</strong></p>
  
  <p>I have a form control orderNo. 
  When I try to do<br>
      <code>this.myForm.controls['orderNo'].setValue = '123';</code><br>
  It works fine and my view is updated with this value.<br>
   But the issue is, I am not able to set the control with null or empty string. Whenever I do<br>
      <code>this.myForm.controls['orderNo'].setValue = null;</code><br>
      or<br>
      <code>this.myForm.controls['orderNo'].setValue = '';</code><br>
  it doesn't reflect on my view. 
  But I could see the form control holds that null value.  (ng.probe($0).componentInstance.myForm.controls['orderNo'].value returns null).
   It is just not being reflected on the view. </p>
  
  <p>Please help me with some thoughts. Thank you.</p>