Exclude WooTickets Ticket Category

/**
 * Removes the "tickets" category from the WooCommerce product categories widget.
 *
 * You can drop this into your theme's functions.php file. You *must* change the
 * value of $exclude_id in this function or it is highly unlikely that it will
 * work on your installation.
 *
 * You can find the "tickets" ID by going to Products > Categories and clicking the
 * "Tickets" category. The URL will look like:
 *
 * wp-admin/edit-tags.php?action=edit&taxonomy=product_cat&tag_ID=13&post_type=product
 *                                                         ^^^^^^^^^
 *
 * What we are interested in is what immediately follows tag_ID, in this case 13.
 */
function exclude_wootickets_category($args) {
    // You need to change the value of $exclude_id
    // to the ticket category ID on your installation!
    $exclude_id = 13;

    if (!isset($args['exclude'])) $args['exclude'] = $exclude_id;
    else $args['exclude'] .= ",$exclude_id";

    return $args;
}

add_filter('woocommerce_product_categories_widget_args', 'exclude_wootickets_category');