Fix file processing

src/PHPMailerEnhanced/PHPMailerEnhanced.php

@@ -210,7 +210,8 @@ class PHPMailerEnhanced extends PHPMailer {
 
                 //region Check the link has no protocol (http, cid, etc.) or it's “file”
                 if (preg_match('#^(?:(?<protocol>[a-z][a-z\d+.-]*):)?(?<path>.+)$#i', $link, $match) === 1) {
-                    if (($match['protocol'] ?? '') !== 'file') {
+                    $protocol = $match['protocol'] ?? 'file';
+                    if ($protocol !== '' && $protocol !== 'file') {
                         return $link;
                     }
                     else {