[BUGFIX] Typo in neg_foreign_table in DataPreprocessor

Change-Id: I5f281c99c65a6a3a0d0d527bdd5db02853eb078b
Releases: master, 6.2
Resolves: #68769
Related: #36573
Reviewed-on: http://review.typo3.org/42287


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>