Fix ::getOpenParticipationContainsPerson

1. The filter predicate must return a boolean
2. The $person variable is not needed

src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php

@@ -364,12 +364,13 @@ class AccompanyingPeriod
      */
     public function getOpenParticipationContainsPerson(Person $person): ?AccompanyingPeriodParticipation
     {
-        $collection = $this->getParticipationsContainsPerson($person)->filter(
-            function(AccompanyingPeriodParticipation $participation) use ($person) {
-                if (NULL === $participation->getEndDate()) {
-                    return $participation;
+        $collection = $this
+            ->getParticipationsContainsPerson($person)
+            ->filter(
+                static function(AccompanyingPeriodParticipation $participation): bool {
+                    return null === $participation->getEndDate();
                 }
-            });
+            );
 
         return $collection->count() > 0 ? $collection->first() : NULL;
     }