WC()->cart null or such error fix for wc 3.6.0 or higher

gistfile1.txt

if ( version_compare( WC_VERSION, '3.6.0', '>=' )) {
							require_once( WC_ABSPATH . 'includes/wc-cart-functions.php' );
							require_once( WC_ABSPATH . 'includes/wc-notice-functions.php' );

							if ( null === WC()->session ) {
								$session_class = apply_filters( 'woocommerce_session_handler', 'WC_Session_Handler' );

								// Prefix session class with global namespace if not already namespaced
								if ( false === strpos( $session_class, '\\' ) ) {
									$session_class = '\\' . $session_class;
								}

								WC()->session = new $session_class();
								WC()->session->init();
							}

							/**
							 * For logged in customers, pull data from their account rather than the
							 * session which may contain incomplete data.
							 */
							if ( null === WC()->customer ) {
								if ( is_user_logged_in() ) {
									WC()->customer = new WC_Customer( get_current_user_id() );
								} else {
									WC()->customer = new WC_Customer( get_current_user_id(), true );
								}
							}

							// Load Cart.
							if ( null === WC()->cart ) {
								WC()->cart = new WC_Cart();
							}
						}