[BUGFIX] Language cache is not cleared anymore

The language cache is not cleared anymore due to
wrong condition in the hook method.

Change-Id: If549d57580d05a547f8c879eed31a1f72667c661
Related: #46205
Releases: 6.0, 6.1
Reviewed-on: https://review.typo3.org/19910
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader