code: public UserLogin ensureLoginOnSession(HttpSession session)
  	{
  		if (session.getAttribute(LOGIN_SESSION_ATTRIBUTE) == null)
  			// Fall back on the anonymous user
  			// Save in the "login" session attribute
  			session.setAttribute(LOGIN_SESSION_ATTRIBUTE, new UserLoginImpl(null));
  
  		return (UserLogin) session.getAttribute(LOGIN_SESSION_ATTRIBUTE);
  	}
docs: Makes sure there is a UserLogin on a session; designed to be called by code unrelated to the regular login logic (the
  TemplateExceptionRenderer) to make sure there's at least an anonymous login session set up for that templater
  
  @param session
  
  @return