Fix a (harmless) off-by-one error in code generation that comes up when

doing a DISTINCT query against a virtual table with an OR term in the
WHERE clause and where the ORDER BY clause has 64 or more references to
the result set.  [forum:/forumpost/dfe8084751|Forum post dfe8084751].

FossilOrigin-Name: 04af7ef77043702f93cbff23548610759786893bd3d4d6fc08181e1e249c6663