Limit Slider Revolution's WP_Query to only include Featured Events that have a featured image

functions.php

<?php
/**
 * Limit Slider Revolution's WP_Query to only include Featured Events that have a featured image
 *
 * @link https://theeventscalendar.com/knowledgebase/k/integrating-the-events-calendar-with-slider-revolution-and-essential-grid/
 *
 * Based on https://gist.github.com/cliffordp/30ac2152a8264ef27235b46b7d16332d
 * Similar code for Essential Grid: https://gist.github.com/Camwyn/15e1936639a5ea7b1575b35f252ebd40
 * Same Slider Revolution code except without requirement for being a Featured Event (works for more than just The Events Calendar): https://gist.github.com/Camwyn/d7128fb83074d75e1562adac2735a834
 *
 * Tested working with version 6.5.24
 *
 * `revslider_get_posts` filter is from plugins/revslider/includes/slider.class.php as of version 6.5.24
 *
 * Filter hook only applies to Slider Revolution > Post-Based Slider > Fetch Posts By Categories & Tags
 * or Slider Revolution > Post-Based Slider > Specific Posts > Specific Posts List (CSV of Post IDs)
 * There are others in plugins/revslider/includes/slider.class.php for other queries.
 *
 * @return array
 */
function revslider_post_based_featured_events_w_featured_image( $query, $slider_id ) {

	/* YOU MUST CHANGE THESE TO YOUR OWN SLIDER REVOLUTION SLIDER IDs!!! */
	$slider_ids_to_affect = [ 2, 20, 34 ]; // include IDs of sliders to affect

	// If this slider is not one we want to affect, bail.
	if ( ! isset( $slider_id, array_reverse( $slider_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 = [];
	}

	// do the filtering...

	// Restrict to events(posts) that have a featured image.
	$meta_query[] = [
		'compare' => 'BETWEEN',
		'key'     => '_thumbnail_id',
		'value'   => [ 1, PHP_INT_MAX ],
	];

	// Restrict to events(posts) that have are featured events.
	if ( class_exists( 'Tribe__Events__Main' )
		&& class_exists( 'Tribe__Events__Featured_Events' )
		&& in_array( Tribe__Events__Main::POSTTYPE, (array) $query['post_type'] )
	) {
		$meta_query[] = [
			'key'	  => Tribe__Events__Featured_Events::FEATURED_EVENT_KEY,
			'compare' => 'EXISTS',
		];
	}

	$query['meta_query'] = $meta_query;

	return $query;
}

add_filter( 'revslider_get_posts', 'revslider_post_based_featured_events_w_featured_image', 10, 2 );