[BUGFIX] PHP Runtime Notice with declaration of authUser()

Change-Id: I7061a3b7e9eeea3c69ea72b2cfaa7a952afbc11b
Reviewed-on: http://review.typo3.org/32168
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>