[Bug?] (ver9.1.0) JOIN between NULLs does not work correctly

[hiroyuki0415]

NULL = NULL appears to evaluate to true

SELECT   e.logicalname,
         e.collectionschemaname,
         e2.logicalname,
         e2.collectionschemaname
FROM     metadata.entity AS e
         LEFT OUTER JOIN
         metadata.entity AS e2
         ON e.collectionschemaname = e2.collectionschemaname
ORDER BY e.logicalname, e2.logicalname;