FormEngineValidation configuration was not added in
SelectTreeElement therefore minitems was not validated.

Change-Id: I38fcf1f20c5eeed667bea96130d4295a56790888
Resolves: #70084
Releases: master
Reviewed-on: http://review.typo3.org/43532


Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>