Test email form - Invalid address: (cc): PHPMailer\Exception

Problem/Motivation

When a user doesn't enter anything in CC and BCC fields in the Test email form, then it throws the below error:

Drupal\Core\Entity\EntityStorageException: Invalid address: (cc): in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 846 of /var/www/d8/docroot/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).
    

PHPMailer\PHPMailer\Exception: Invalid address: (cc): in PHPMailer\PHPMailer\PHPMailer->addOrEnqueueAnAddress() (line 1081 of /var/www/d8/vendor/phpmailer/phpmailer/src/PHPMailer.php).

Steps to reproduce

1. Enable the Reroute EMail module.
2. Navigate to the Test Email Form.
3. Enter the To email address as it's mandatory field and keep the cc & bcc fields as is.
4. Submit the form and you will get The website encountered an unexpected error. issue.

The reason it sends empty CC and BCC values but SMTP/PHPMailer modules expect headers which has both key & value.

Array
(
    [cc] => 
    [bcc] => 
    [subject] => Reroute Email Test
    [body] => Reroute Email Body
)

Proposed resolution

Need to unset the keys which have empty values. For example: in the above case, CC & BCC should not be part of the params array, if empty.