message: Fix relative path to current directory being empty case for windows file system CreateDir function.
diff: @@ -439,6 +439,9 @@ Status WindowsFileSystem::DeleteFile(const string& fname) {
  Status WindowsFileSystem::CreateDir(const string& name) {
  Status result;
  std::wstring ws_name = Utf8ToWideChar(name);
  + if (ws_name.empty()) {
  + return errors::AlreadyExists(name);
  + }
  if (_wmkdir(ws_name.c_str()) != 0) {
  result = IOError("Failed to create a directory: " + name, errno);
  }
  