Tell FacetWP to skip SearchWP when an empty s query parameter is passed

functions.php

<?php

// Tell FacetWP to disregard SearchWP if the search query is empty.
add_filter( 'facetwp_facets', function( $facets ) {
	if ( ! isset( $_REQUEST['s'] ) || ! empty( $_REQUEST['s'] ) || empty( $facets ) || ! is_array( $facets ) ) {
		return $facets;
	}

	foreach ( $facets as $key => $facet ) {
		if ( 'search' !== $facet['type'] ) {
			continue;
		}

		// Because there's an empty s query parameter we can just tell FacetWP
		// that SearchWP should be disregarded and to fall back to WP native handling.
		$facets[ $key ]['search_engine'] = '';
	}

	return $facets;
}, 5 );