`hfile-hash-join`: no value found for key

[bel28kent]

When hfile-hash-join is called on scriabin-op66.krn (through autowedge composition), it returns "no value found for key."

The error persists when the behavior is isolated from autowedge but goes away when the hfile is not converted to ab-hgraph, so the problem is somewhere in hfile->ab-hgraph, or ab-hgraph->hfile.

The length of hfile records is one longer than the length of the scriabin file, so somewhere an extra line is being added.