[BUGFIX] getLabelsFromItemsList() retuns no value when no item found

BackendUtility::getLabelsFromItemsList() does not take
itemsProcFunc into account. This means no value is
returned when there is no matching item found.

With this change the plain db value is returned
when no matching item is found.

Resolves: #54131
Releases: 6.2, 6.1
Change-Id: Ieb04394fa104627b765f6bc05d0d5886f29099c9
Reviewed-on: https://review.typo3.org/25866
Reviewed-by: Andreas Wolf
Tested-by: Andreas Wolf