code: @Nonnull
    public static Charset getCharsetFromMimeTypeOrDefault (@Nullable final IMimeType aMimeType)
    {
      final Charset ret = MimeTypeHelper.getCharsetFromMimeType (aMimeType);
      return ret != null ? ret : CSSDataURLHelper.DEFAULT_CHARSET;
    }
docs: Determine the charset from the passed MIME type. If no charset was found,
  return the default charset.
  
  @param aMimeType
  The MIME type to investigate.
  @return Never <code>null</code>.