Event Featured image defaults to venue Featured image then to a Defaults URL

functions.php

<?php
/*
 * If you already have something in your functions.php, please remove these first few lines
 */
add_filter( 'tribe_event_featured_image', 'tec_forum_938271', 11, 3 );

function tec_forum_938271( $featured_image, $post_id, $size ){
	if ( ! empty( $featured_image )  ){
		return $featured_image;
	}

	if ( ! tribe_is_event( $post_id ) ){
		return $featured_image;
	}

	$event = get_post( $post_id );

	$venue = get_post( tribe_get_venue_id( $event->ID ) );

	$venue_featured = wp_get_attachment_image_src( get_post_thumbnail_id( $venue->ID ), $size );

	if ( ! empty( $venue_featured ) ){
		$image_url = $venue_featured[0];
	} else {
		// Default URL
		$image_url = 'http://placehold.it/300x300';
	}
	$featured_image .= '<div class="tribe-events-event-image"><img src="' . $image_url . '" title="' . get_the_title( $event->ID ) . '" alt="' . get_the_title( $event->ID ) . '" /></div>';

	return $featured_image;
}