Warning: Missing argument 2 for WC_Memberships_Member_Discounts

How do I cope with “Warning: Missing argument 2 for WC_Memberships_Member_Discounts” At first I only installed a shipping method, and then I tried to shopping and the error occurs. But when resuming “Place Order” successful booking.

Problems in the following line of code:

    public function refresh_cart_upon_member_login( $user_login, $user ) {

    // small "hack" to trigger a refresh in cart contents
    // that will set any membership discounts to products that apply
    if ( $user_login && wc_memberships_is_user_active_member( $user, null, false ) ) {

        $this->reset_cart_session_data();
    }
}

The following php code http://pastebin.com/mcHYTd27 (See Line 1309)

Please Help Me Thanks ^_^