featured-fix-shortcode.php

<?php
add_filter( 'tribe_events_pro_shortcode_tribe_events_validate_arguments_map', function( $map, $shortcode ) {
	$map['featured'] = function( $value ) {
		if ( null === $value || 'null' === $value ) {
			return null;
		}

		return tribe_is_truthy( $value );
	};
	return $map;
}, 15, 2 );

add_filter( 'tribe_events_pro_shortcode_tribe_events_default_arguments', function( $default_arguments, $shortcode ) {
	$default_arguments['featured'] = null;
	return $default_arguments;
}, 15, 2 );