do not add referrer if user is null

src/Bundle/ChillPersonBundle/EventListener/AccompanyingPeriodWorkEventListener.php

@@ -25,6 +25,8 @@ class AccompanyingPeriodWorkEventListener
 
     public function prePersistAccompanyingPeriodWork(AccompanyingPeriodWork $work): void
     {
+        if (null !== $this->security->getUser()) {
             $work->addReferrer($this->security->getUser());
         }
+    }
 }