[BUGFIX] Fix PHP 8 warnings in DataHandler

Moved assignment of $destPid = $sortInfo['pid'] after check if
$sortInfo is an array, since the method call to getSortNumber
can return other values than an array.

Resolves: #101606
Releases: main, 12.4, 11.5
Change-Id: I3cfef35b351a0cd1fa8197702cce9e3b05871fcf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80430


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>