Update to fix #53

I changed the condition of when the Select2Choice/Select2MultiChoice renderInitializationScript gets executed. In our application we have a page with a select2choice component and a panel with some kind of user search. When I submit the user search and afterwards repaint the dropdown with an ajax event from another request the dropdown is blank and does no longer show the previously selected value. 

In the debugger I can see that hasRawInput() on the Select2Choice component returns true as the input of the previous search submit is still set. The repaint event however happens in another request and therefore the following call to convertInput() will set a null value on the component as the parameter is not in the current request.