`ab-hgraph->hfile` is failing on `spine-splits-left-joins-right`

[bel28kent]

(check-expect (ab-hgraph->hfile
               (ab-hgraph (root (list (list (leaf (token  "**kern" EXCLUSIVE-INTERPRETATION 0))
                                            (parent (token  "*^" SPINE-SPLIT 1)
                                                    (list (parent (token  "*^" SPINE-SPLIT 2)
                                                                  (list (leaf (token  "4c" SPINE-DATA 3))
                                                                        (leaf (token  "4c" SPINE-DATA 4))
                                                                        (leaf (token  "4c" SPINE-DATA 5))
                                                                        (leaf (token  "*" NULL-INTERPRETATION 6))
                                                                        (leaf (token  "*v" SPINE-JOIN 7)))
                                                                  (list (leaf (token  "4c" SPINE-DATA 3))
                                                                        (leaf (token  "4c" SPINE-DATA 4))
                                                                        (leaf (token  "4c" SPINE-DATA 5))
                                                                        (leaf (token  "*v" SPINE-JOIN 6))))
                                                          (leaf (token  "*v" SPINE-JOIN 7)))
                                                    (list (leaf (token  "*" NULL-INTERPRETATION 2))
                                                          (leaf (token  "4c" SPINE-DATA 3))
                                                          (leaf (token  "4c" SPINE-DATA 4))
                                                          (leaf (token  "4c" SPINE-DATA 5))
                                                          (leaf (token  "*v" SPINE-JOIN 6))))
                                            (leaf (token  "*-" SPINE-TERMINATOR 8)))))))
              (path->hfile "../../data/order/spine-splits-left-joins-right.krn"))