fix data provider which randomly generate invalid data in test

src/Bundle/ChillPersonBundle/Tests/Controller/AccompanyingCourseApiControllerTest.php

@@ -555,7 +555,8 @@ class AccompanyingCourseApiControllerTest extends WebTestCase
 
         $personIds = $em->createQuery("SELECT p.id FROM ".
             Person::class." p ".
-            " WHERE p.center = :center")
+            " WHERE p.center = :center ".
+            " AND SIZE(p.accompanyingPeriodParticipations) > 0 ")
             ->setParameter('center', $center)
             ->setMaxResults($maxResults)
             ->getScalarResult();