function wp_kses_normalize_entities3( $matches ) {
  if ( empty( $matches[1] ) ) {
    return '';
  }

  $hexchars = $matches[1];

  return ( ! valid_unicode( hexdec( $hexchars ) ) ) ? "&#x$hexchars;" : '&#x' . ltrim( $hexchars, '0' ) . ';';
}