Ensure that Mandrill mail responses are checked if they are arrays

@@ -271,7 +271,8 @@ function send_triggered_notification($uid = 0, $trigger = "NO_TRIGGER", $args =
             if (CBV\system_can_send_emails()) {
                 $response = \wpMandrill::mail($to_email, $subject, !empty($html) ? $html : $alttext, [], $attachments);
                 if (
-                    isset($response[0]['status'])
+                    is_array($response)
+                    && isset($response[0]['status'])
                     && isset($response[0]['status'])
                     && !in_array($response['status'], ['rejected', 'invalid'])
                 ) {