EDIT

ref #8476: disable flat flag if tree has subtrees

ref #8476: do not allow d&d to a child

ref #8476: do not show create child if tree is flat

fix #9636 fix NPE in DeterminationDetailElement

cleanup and set cancelable to true SetXXXForSubtreeOperations

ref #9630: avoid IAE continue

ref #9629: handle OptionalDataException - continue

ref #9630: make computed descriptions handling configurable - avoid IAE

ref #9629: handle OptionalDataException

ref #9630: make computed descriptions handling configurable - adapt content and label provider