[BUGFIX] Only variables should be passed by reference

array_shift() takes argument by reference.

Releases: 6.2
Fixes: #54933
Change-Id: I94c16bc739f36d669640701561ff94aebd63b1f5
Reviewed-on: https://review.typo3.org/26779
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind