WL-3653 Announcements tool broken for anonymous.

Some recent changes mean that the announcement tool is broken for the anonymous user as when there isn’t anyone logged in the user ID returned from the session manager is null which is then compared with the current user ID which for the anonymous user is an empty string. The user directory service will return an empty string for the anonymous user.
Merge pull request #9 from ox-it/WL-3653

WL-3653 Announcements tool broken for anonymous.