I have an error in the file error_log

[01-Sep-2017 02:39:40 UTC] id was called incorrectly. Product properties should not be accessed directly. Backtrace: require('wp-blog-header.php'), require_once('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('wp_loaded'), WP_Hook->do_action, WP_Hook->apply_filters, call_user_func_array, WC_Cart->init, WC_Cart->get_cart_from_session, WC_Product->is_purchasable, apply_filters('woocommerce_is_purchasable'), WP_Hook->apply_filters, call_user_func_array, som_disable_repeat_purchase, WC_Abstract_Legacy_Product->__get, wc_doing_it_wrong. This message was added in version 3.0.

This is line error
if ( $downloads = WC()->customer->get_downloadable_products() ) {

Please fix it, thank