Followup to r1467230.

* subversion/libsvn_subr/subst.c
  (translate_keyword_subst): Adjust test as well as assignment.

Found by: rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1467236 13f79535-47bb-0310-9956-ffa450edef68