[BUGFIX] Handle new record correctly in selectTree form element

Pass command (edit/new) from input data attribute
to SelectTreeController.

Resolves: #77621
Releases: master
Change-Id: I58b5099402cbce3f50a2681eefa6ab4bba263a56
Reviewed-on: https://review.typo3.org/49577


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>