Fatal error because of the extension

Hello,
I would like to send you an error report generated because of the extension so that you can integrate it in your future updates.

Si vous cherchez de l’aide pour ce problème, les informations suivantes pourraient vous être demandées :
WordPress version 5.8.1
Thème actuel : Bard (version 1.93)
Extension actuelle : Email Users (version 4.8.8)
PHP version 8.0.9

Détails de l’erreur
======================
Une erreur de type E_ERROR a été causée dans la ligne 1545 du fichier /home/objesubs/public_html/wp-content/plugins/email-users/email-users.php. Message d’erreur : Uncaught TypeError: Cannot access offset of type string on string in /home/objesubs/public_html/wp-content/plugins/email-users/email-users.php:1545
Stack trace:
#0 /home/objesubs/public_html/wp-content/plugins/email-users/email_users_group_mail_form.php(122): mailusers_get_roles()
#1 /home/objesubs/public_html/wp-content/plugins/email-users/email_users_send_group_mail.php(247): include('/home/objesubs/...')
#2 /home/objesubs/public_html/wp-content/plugins/email-users/email-users.php(532): require_once('/home/objesubs/...')
#3 /home/objesubs/public_html/wp-includes/class-wp-hook.php(303): mailusers_send_to_group_page()
#4 /home/objesubs/public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters()
#5 /home/objesubs/public_html/wp-includes/plugin.php(470): WP_Hook->do_action()
#6 /home/objesubs/public_html/wp-admin/admin.php(259): do_action()
#7 {main}
  thrown