Crash using partial-order

[philzook58]

The following was part of an encoding of an intuitionistic Kripke model.

(declare-sort World)
(define-fun R ((x World) (y World)) Bool ((_ partial-order 0) x y))

(declare-sort Atom)
(declare-fun value (World Atom) Bool)
(declare-const w World)
(assert (R w w))

(assert
  (forall ((p Atom) (u World) (w World))
  (=>
    (and (value w p) (R w u))
    (value u p)
  )
  )
)

(check-sat)
(get-model)

on Z3 version 4.10.2 - 64 bit it crashes with the message

terminate called after throwing an instance of 'std::bad_variant_access'
  what():  Unexpected index
Aborted (core dumped)