[BUGFIX] Fix possible sql injections in category migration

Change-Id: Ica251617f6d746a8ae94f8cbec075a833f6ff317
Reviewed-on: http://review.typo3.org/31895
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>