fix: setAttachmentCID() does not work with buffer string

Author: kenjis

system/Email/Email.php

@@ -705,13 +705,23 @@ public function attach($file, $disposition = '', $newname = null, $mime = '')
     public function setAttachmentCID($filename)
     {
         foreach ($this->attachments as $i => $attachment) {
+            // For file path.
             if ($attachment['name'][0] === $filename) {
                 $this->attachments[$i]['multipart'] = 'related';
 
                 $this->attachments[$i]['cid'] = uniqid(basename($attachment['name'][0]) . '@', true);
 
                 return $this->attachments[$i]['cid'];
             }
+
+            // For buffer string.
+            if ($attachment['name'][1] === $filename) {
+                $this->attachments[$i]['multipart'] = 'related';
+
+                $this->attachments[$i]['cid'] = uniqid(basename($attachment['name'][1]) . '@', true);
+
+                return $this->attachments[$i]['cid'];
+            }
         }
 
         return false;