code: @Nonnull
    public static FileIOError deleteDirRecursiveIfExisting (@Nonnull final Path aDir)
    {
      final FileIOError aError = deleteDirRecursive (aDir);
      if (aError.getErrorCode ().equals (EFileIOErrorCode.SOURCE_DOES_NOT_EXIST))
        return aError.withoutErrorCode ();
      return aError;
    }
docs: Delete an existing directory including all child objects if it is existing.
  
  @param aDir
  The directory to be deleted. May not be <code>null</code>.
  @return A non-<code>null</code> error code.