Limit Essential Grid's WP_Query to only include Featured Events that have a featured image

functions.php

<?php
/**
 * Limit Essential Grid's WP_Query to only include Featured Events that have a featured image
 *
 * @link https://theeventscalendar.com/knowledgebase/featured-events/
 *
 * From https://gist.github.com/cliffordp/a6aad3c60f469970b1ecb209d85ec755
 * Similar code for Slider Revolution: https://gist.github.com/cliffordp/30ac2152a8264ef27235b46b7d16332d
 * Same Essential Grid code except without requirement for being a Featured Event (works for more than just The Events Calendar): https://gist.github.com/cliffordp/fbbaad70b9b8748819ac73f00260ac5e
 *
 * essgrid_get_posts filter is from /wp-content/plugins/essential-grid/includes/base.class.php
 *
 * Tested working with version 2.1.0.2
 *
 * Filter hook only applies to Essential Grid > Source > Source Based on Posts, Pages, Custom Posts
 *
 * @return array
 */
function essgrid_post_based_featured_events_w_featured_image( $query, $grid_id ) {

	/*
	 * YOU MUST CHANGE THESE
	 * TO YOUR OWN ESSENTIAL GRID
	 * GRID IDs
	 * !!!
	 */
	$grid_ids_to_affect = array( 1, 2, 14 ); // include IDs of grids to affect

	// if this grid is not one to affect, do no filtering
	if ( ! in_array( $grid_id, $grid_ids_to_affect ) ) {
		return $query;
	}

	// get the existing meta_query so we aren't wiping that out
	if ( ! empty( $query['meta_query'] ) ) {
		$meta_query = (array) $query[ 'meta_query' ];
	} else {
		$meta_query = array();
	}

	// do the filtering...

	// has a Featured Image
	$meta_query[] = array(
		'key' => '_thumbnail_id',
		'compare' => 'EXISTS',
	);

	// is a Featured Event (requires The Events Calendar version 4.4+ from January 9, 2017)
	if ( class_exists( 'Tribe__Events__Main' )
	     && class_exists( 'Tribe__Events__Featured_Events' )
	     && Tribe__Events__Main::POSTTYPE === $query['post_type']
	) {
		$meta_query[] = array(
			'key'     => Tribe__Events__Featured_Events::FEATURED_EVENT_KEY,
			'compare' => 'EXISTS',
		);
	}

	$query['meta_query'] = $meta_query;

	return $query;
}

add_filter( 'essgrid_get_posts', 'essgrid_post_based_featured_events_w_featured_image', 10, 2 );