Just wondering how to fix this to not make Pro Editor not work. Here’s what I have:
if (!(is_admin() )) {
	function defer_parsing_of_js ( $url ) {
		if ( FALSE === strpos( $url, '.js' ) ) return $url;
		if ( strpos( $url, 'jquery.js' ) ) return $url;
		if ( strpos( $url, 'x-head.min.js' ) ) return $url;
		return "$url' defer='defer";
	}
	add_filter( 'clean_url', 'defer_parsing_of_js', 11, 1 );
}