[BUGFIX] Fix wrong target type in File Converter

Change-Id: I688b794ff57c1e27e4e39f18c0b1026e8de1217a
Reviewed-on: http://review.typo3.org/32575
Reviewed-by: Fabien Udriot <fabien.udriot@ecodev.ch>
Tested-by: Fabien Udriot <fabien.udriot@ecodev.ch>