message: tests: Allow document_load_file_special_folder to load empty document
  On some Debian systems it looks like we *can* open the current folder as
  a file and read its contents, but parsing the result produces an empty
  document. We now handle this case as well.
  Fixes
diff: @@ -596,7 +596,8 @@ TEST(document_load_file_special_folder)
  xml_document doc;
  xml_parse_result result = doc.load_file(".");
  // status_out_of_memory is somewhat counter-intuitive but on Linux ftell returns LONG_MAX for directories
  - CHECK(result.status == status_file_not_found || result.status == status_io_error || result.status == status_out_of_memory);
  + // on some Debian systems the folder is also read as empty, hence status_no_document_element check
  + CHECK(result.status == status_file_not_found || result.status == status_io_error || result.status == status_out_of_memory || result.status == status_no_document_element);
  }
  #endif
  