Fixed a few bugs

- When the field "title" is a PageTitleLanguage fields, the page
title is an object and needs to be casted to string.
- The UserGroupsHooks was creating a fatal error when trying to
edit user profile.
Merge pull request #28 from rlanvin/pagetitlelanguagefix

Fixed to support PageTitleLanguage. Fixed fatal error when saving users.
Don't try to process data that isn't there