解析

@@ -133,7 +133,7 @@ class Header{
      */
     public function getTo(bool $isArray = false):array {
         // 如果有这个字段，就用这个字段  to字段的邮箱可能被伪造
-        $to = $this->attributes['to']??$this->attributes['delivered-to'];
+        $to = $this->attributes['to']??($this->attributes['delivered-to']??'');
 
         return $this->parseAddress($to,$isArray);
     }