Fix issue that generates exception with Pattern and viewPattern when getSubject returns None

Instead of using "deadboltHandler.getSubject(request).get", it's necessary to take into account the case where getSubject returns None with a matching pattern.
The change is simple and has been tested on local (after reading the process explain at http://www.objectify.be/wordpress/?p=363) with the deadbolt-2-scala-examples project by forcing getSubject to return None. 
NB: in this case it remains some issues due to the inappropriate use of .get in the views