OptionalsortedOptionaltroveTroveManager.getTroveOwnersCount() and SortedTroves.getSize(), for the last Trove gate
(MK-074). Both optional on the same rule previewOpen.troveStatus follows (MK-047):
undefined is "not asked", not "there is one", so the gate is simply not evaluated and
not reported. previewClose always supplies them.
Everything evaluateClose needs, already read from the chain.