Filter empty/invalid orders when refunded orders returns false values.

remove-empty-wc-orders.php

<?php

// Filter the orders returned by WooCommerce so that any missing ones are removed from the list.
add_filter( 'woocommerce_order_query', static function( $posts ) {
	// For some reason, $posts may not be an array. Some other plugin(s) may be using the filter incorrectly.
	if ( is_array( $posts ) ) {
		$posts = array_filter( $posts );
	}

	return $posts;
} );