Using PHP 8.1 we have an issue when we don't have the value for the mailchimp_rules_api_key
variable.
mailchimp_rules_api_key
Drupal variable should not be available.Error:
explode(): Passing null to parameter #2 ($string) of type string is deprecated in [libraries]/vendor/thinkshout/mailchimp-api-php/src/Mailchimp.php line 302
Send the only string-converted API key to the Mailchimp.