Fix the second part of issue #3641.
Fix the second part of issue #3641.

Note: this passes tests, but in pre-commit review I suspect the new 'if'
could be improved, so please review.

* subversion/libsvn_repos/replay.c
  (add_subdir):
    Don't call add_subdir() when there is no history to convert
    to a history-less add.  (Thanks, docstrings.)

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1063573 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion