diff --git a/server/controllers/ticket/comment.php b/server/controllers/ticket/comment.php
index 5b250812..7be2b248 100755
--- a/server/controllers/ticket/comment.php
+++ b/server/controllers/ticket/comment.php
@@ -141,7 +141,7 @@ class CommentController extends Controller {
 
         $email = $recipient['email'];
         $name = $recipient['name'];
-        $isStaff = $recipient['staff'];
+        $isStaff = array_key_exists('staff', $recipient) && $recipient['staff'];
 
         $url = Setting::getSetting('url')->getValue();
 
diff --git a/server/models/Ticket.php b/server/models/Ticket.php
index 702afeec..f407ab02 100755
--- a/server/models/Ticket.php
+++ b/server/models/Ticket.php
@@ -188,7 +188,7 @@ class Ticket extends DataStore {
             if(!Controller::isStaffLogged() && $ticketEvent->private) {
                 continue;
             }
-    
+
             $events[] = $event;
         }
 
@@ -200,12 +200,13 @@ class Ticket extends DataStore {
     }
 
     public function isAuthor($user) {
+        if(!$user->isNull()) return false;
         $ticketAuthor = $this->authorToArray();
         if(is_string($user)) return $user == $ticketAuthor['email'];
         return $user->id == $ticketAuthor['id'] && ($user instanceof Staff) == $ticketAuthor['staff'];
     }
 
     public function isOwner($user) {
-        return $this->owner && $user->id == $this->owner->id && ($user instanceof Staff);
+        return !$user->isNull() && $this->owner && $user->id == $this->owner->id && ($user instanceof Staff);
     }
 }