WP Mailster v1.8.22

[Bug Fix] Fix issue where apostrophe character within SMTP error code makes it that send errors are not stored, closing SQL injection attack vector
[Bug Fix] Fix PHP Deprecated: strripos(): Passing null to parameter in MailUtils.php
[Bug Fix] Fix for thread/references shortening
[Bug Fix] Prevent PHP warning (array_key_exists(): Argument #2 ($array) must be of type array, null given)) when a sender without TO recipient is received