error in cvs head: bogus varattno for OUTER var: 5

The attached sql file creates some table infrastructure and then tries to
explain a query. I get the following error on CVS HEAD:

psql:bogus_varattno_error.sql:23: ERROR: bogus varattno for OUTER var: 5

In my real data, when I attempt to run the query I get the error:
ERROR: invalid attribute number 5

But in the test setup it just returns an empty set.

Any ideas what is causing this? Is it my query, or is something broken
somewhere? I tend to think the latter, since this error message does not
feel like one that a user would get and be expected to know what to do
with...

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Ears.