title: Spring Roo How add an empty option to a combo
body: <p>Adding an empty option  is very easy to do in normal HTML/JSP page. But I am using spring roo and the GUI tag libraries it offers.
  I need to add an empty option to the combox and be able to validate if a user has slected a non empty  option in this combo box or not. The code generated by Spring roo doesn't have this and first option of my combo box appears to be a non empty option.
  Any idea how to extend this behavior and how to do the validation or client and server sides?</p>