PHP 8.0.16 Fatal Error

The plugin is not working with PHP 8.0.16 — throws a Fatal error.

[21-Mar-2022 06:06:29 UTC] PHP Fatal error:  Uncaught TypeError: array_merge(): Argument #2 must be of type array, null given in /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php:207
Stack trace:
#0 /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php(207): array_merge()
#1 /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/wc-sendinblue-api.php(62): SibApiClient->getAllEmailTemplates()
#2 /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/wc-sendinblue.php(74): WC_Sendinblue_API::get_templates()
#3 /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/woocommerce-sendinblue.php(351): WC_Sendinblue::init()
#4 /wp-includes/class-wp-hook.php(307): WC_Sendinblue_Integration->load_customizations()
#5 /wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#6 /wp-includes/plugin.php(474): WP_Hook->do_action()
#7 /wp-content/plugins/woocommerce/includes/class-woocommerce.php(633): do_action()
#8 /wp-includes/class-wp-hook.php(307): WooCommerce->init()
#9 /wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#10 /wp-includes/plugin.php(474): WP_Hook->do_action()
#11 /wp-settings.php(587): do_action()
#12 /wp-config.php(108): require_once('...')
#13 /wp-load.php(50): require_once('...')
#14 /wp-admin/admin.php(34): require_once('...')
#15 {main}
  thrown in /wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php on line 207

If we switch to PHP 7.4 these are the warnings:

[21-Mar-2022 06:40:24 UTC] PHP Notice:  Undefined index: templates in /public_html/wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php on line 214

[21-Mar-2022 06:40:24 UTC] PHP Warning:  array_merge(): Expected parameter 2 to be an array, null given in /public_html/wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php on line 214

[21-Mar-2022 06:40:24 UTC] PHP Warning:  count(): Parameter must be an array or an object that implements Countable in /public_html/wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/SibApiClient.php on line 217

[21-Mar-2022 06:40:27 UTC] PHP Notice:  Undefined offset: 0 in /public_html/wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/wc-sendinblue-settings.php on line 225

[21-Mar-2022 06:40:27 UTC] PHP Notice:  Trying to access array offset on value of type null in /public_html/wp-content/plugins/woocommerce-sendinblue-newsletter-subscription/includes/wc-sendinblue-settings.php on line 225