Fix problem where 'bk parent' prints bogus error about an invalid filehandle when there is no parent.
Fix problem where 'bk parent' prints bogus error about an invalid filehandle
when there is no parent.

BUGID: 2002-09-13-002

bk: 3d948b4aAb4iigOJY6XMAUilbyegsQ
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper