Error Trying to access array offset while activating WordPress debug

i do define( 'WP_DEBUG', true ); in public_html/wp-config.php and I saw this error messag in wp-admin

Notice: Trying to access array offset on value of type bool in /home/urbanit1/public_html/wp-content/plugins/no-captcha-recaptcha-for-woocommerce/base-class.php on line 24

line 24 in base-class.php :

self::$site_key = self::$plugin_options['site_key'];

Please help to solve this problem

code:

<?php


class WC_Ncr_No_Captcha_Recaptcha {

    /** @var string captcha site key */
    static private $site_key;

    /** @var string captcha secrete key */
    static private $secret_key;

    static private $theme;

    static private $language;

    static protected $error_message;

    static protected $plugin_options;

    public static function initialize() {

        self::$plugin_options = get_option( 'wc_ncr_options' );

        self::$site_key = self::$plugin_options['site_key'];

        self::$secret_key = self::$plugin_options['secrete_key'];

        self::$theme = self::$plugin_options['theme'];

        self::$language = self::$plugin_options['language'];

        self::$error_message = self::$plugin_options['error_message'];


        add_action( 'plugins_loaded', array( __CLASS__, 'load_plugin_textdomain' ) );

        // initialize if login is activated
        if ( ( isset( self::$plugin_options['captcha_wc_registration'] ) && self::$plugin_options['captcha_wc_registration'] == 'yes' ) || ( isset( self::$plugin_options['captcha_wc_login'] ) && self::$plugin_options['captcha_wc_login'] == 'yes' ) || ( isset( self::$plugin_options['captcha_wc_password_reset'] ) && self::$plugin_options['captcha_wc_password_reset'] == 'yes' ) ) {
            add_action( 'wp_head', array( __CLASS__, 'header_script' ) );
        }
    }

    public static function load_plugin_textdomain() {
        load_plugin_textdomain( 'wc-no-captcha', false, basename( dirname( __FILE__ ) ) . '/languages/' );
    }

    /** reCAPTCHA header script */
    public static function header_script() {

        $lang_option = self::$plugin_options['language'];

        // if language is empty (auto detected chosen) do nothing otherwise add the lang query to the
        // reCAPTCHA script url
        if ( isset( $lang_option ) && ( ! empty( $lang_option ) ) ) {
            $lang = "?hl=$lang_option";
        } else {
            $lang = null;
        }

        echo '<script src="https://www.google.com/recaptcha/api.js' . $lang . '" async defer></script>' . "\r\n";
    }


    /** Output the reCAPTCHA form field. */
    public static function display_captcha() {

        echo '<div class="g-recaptcha" data-sitekey="' . self::$site_key . '" data-theme="' . self::$theme . '"></div>';
    }

    /**
     * Send a GET request to verify captcha challenge
     *
     * @return bool
     */
    public static function captcha_wc_verification() {

        $response = isset( $_POST['g-recaptcha-response'] ) ? esc_attr( $_POST['g-recaptcha-response'] ) : '';

        $remote_ip = $_SERVER["REMOTE_ADDR"];

        // make a GET request to the Google reCAPTCHA Server
        $request = wp_remote_get(
            'https://www.google.com/recaptcha/api/siteverify?secret=' . self::$secret_key . '&response=' . $response . '&remoteip=' . $remote_ip
        );

        // get the request response body
        $response_body = wp_remote_retrieve_body( $request );

        $result = json_decode( $response_body, true );

        return $result['success'];
    }


    public static function on_activation() {
        if ( ! current_user_can( 'activate_plugins' ) ) {
            return;
        }
        $plugin = isset( $_REQUEST['plugin'] ) ? $_REQUEST['plugin'] : '';
        check_admin_referer( "activate-plugin_{$plugin}" );

        $default_options = array(
            'captcha_wc_registration' => 'yes',
            'captcha_wc_comment'      => 'yes',
            'theme'                => 'light',
            'error_message'        => __('<strong>ERROR</strong>: Please confirm you are not a robot', 'wc-no-captcha')
        );

        add_option( 'wc_ncr_options', $default_options );
    }

    public static function on_uninstall() {
        if ( ! current_user_can( 'activate_plugins' ) ) {
            return;
        }

        delete_option( 'wc_ncr_options' );
    }
}