Ensure that failures to construct a window key will result in defined cache access behavior. We use the latest cache API improvements to skip cache access in that case.
Ensure that failures to construct a window key will result
in defined cache access behavior. We use the latest cache
API improvements to skip cache access in that case.

* subversion/libsvn_fs_fs/fs_fs.c
  (get_window_key): return NULL instead of "" upon failure

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1243284 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion