WP/WC missing argument in WooCommerce Function

if (!is_user_logged_in()) {    //determine WordPress user account to impersonate    $user_login = 'guest';    //get user ID    $user = get_userdatabylogin($user_login); // below WP 3.3.0    //$user =  get_user_by('login', $user_login); above or equals WP 3.3.0    $user_id = $user->ID;    //login    wp_set_current_user($user_id, $user_login);    wp_set_auth_cookie($user_id);    do_action('wp_login', $user_login);}

There is a hook in WooCommerce like this.

add_action( 'wp_login', 'wc_maybe_store_user_agent', 10, 2 );

The "wc_maybe_store_user_agent" expects 2 parameter. If the user ID is not set, it will show the error you mentioned.Test my snippet above

Function is at line 1516 in plugins/woocommerce/includes/wc-core-functions.php

function wc_maybe_store_user_agent( $user_login, $user ) {    if ( 'yes' === get_option( 'woocommerce_allow_tracking', 'no' ) && user_can( $user, 'manage_woocommerce' ) ) {        $admin_user_agents   = array_filter( (array) get_option( 'woocommerce_tracker_ua', array() ) );        $admin_user_agents[] = wc_get_user_agent();        update_option( 'woocommerce_tracker_ua', array_unique( $admin_user_agents ) );    }}add_action( 'wp_login', 'wc_maybe_store_user_agent', 10, 2 );

You missed one parameter. Try this.

do_action( 'wp_login', $user->user_login, $user );

Source: https://developer.wordpress.org/reference/hooks/wp_login/