Properly check for array-type before accessing
or counting the variable.

Resolves: #52045
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Change-Id: Id161fddadbbcadd462de36e8227278107f2e7a3a
Reviewed-on: https://review.typo3.org/23857
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Reviewed-by: Markus Klein
Tested-by: Markus Klein