[BUGFIX] Use correct value for eventPid in DataHandler

When using workspaces and the record properties
should be shown, the wrong field (_ORIG_pid instead of
t3ver_oid) is used. This is introduced by
a cleanup patch of mine 1y ago, where an accidental
null coalescense evaluation is used.

Resolves: #86868
Related: #82769
Releases: master
Change-Id: I2505f103608350f37c6bf769de4368b62ed67d55
Reviewed-on: https://review.typo3.org/58857


Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Achim Fritz <af@achimfritz.de>
Tested-by: Achim Fritz <af@achimfritz.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>