RSS Graffiti doesn't find images

I’m using this function to get post images transmitted to Facebook via RSS Graffiti.

function insert_fb_in_head() {
	global $post;
	...
	if(!has_post_thumbnail( $post->ID )) {
		$default_image="/wp-content/themes/smmp2014/images/smmp-icon.png";
		//replace this with a default image on your server or an image in your media library
		echo '<meta property="og:image" content="' . $default_image . '"/>';
	}else{
		$thumbnail_src = wp_get_attachment_image_src( get_post_thumbnail_id(
		$post->ID ), 'medium' );
		echo '<meta property="og:image" content="' . esc_attr( $thumbnail_src[0]
		) . '"/>';
	}
	echo "\n";
}
add_action( 'wp_head', 'insert_fb_in_head' );

That doesn’t work anymore with BJ Lazy Load.

Any suggestion would be highly appreciated.

https://www.ads-software.com/plugins/bj-lazy-load/