[BUGFIX] Insufficient array check

In Service\DataHandling\DataHandler::checkRecordUpdateAccess(),
a is_array() call throws a warning in PHP 5.4+. It tries to check
the second dimension of the given array,
but the variable may not be an array at all.

Resolves: #61637
Releases: 2.0, 1.9
Change-Id: I30d3567b0bb23bf5f207fcc62a13c39f04155721
Reviewed-on: http://review.typo3.org/32800
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>