Simplify some logic

utils/postman.php

@@ -63,10 +63,6 @@ class Activitypub_postman
     public function __construct($from, $to)
     {
         $this->actor = $from;
-
-        if (empty ($to)) {
-            throw new Exception ('You can not summon up a postman without recipients!');
-        }
         $discovery = new Activitypub_explorer();
         $this->to = $to;
         $followers = apActorFollowersAction::generate_followers($this->actor, 0, null);