* subversion/libsvn_fs_fs/transaction.c
  (svn_fs_fs__add_change): Don't try to duplicate NULL strings.
                           This might not be safe with pre-1.5 APR.

Suggested by: julianfoad


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1631051 13f79535-47bb-0310-9956-ffa450edef68