fix: only use destination's pickup values

src/Twig/AppRuntime.php

@@ -50,7 +50,7 @@ class AppRuntime implements RuntimeExtensionInterface
         return 'nationality' === $property ? $country->getNationality() : $country->getName();
     }
 
-    public function bpnPickupLabel(?int $id): string
+    public function bpnPickupLabel(?int $id): ?string
     {
         if (null === $id) {
             return 'keine Busbegleitung';
@@ -59,7 +59,7 @@ class AppRuntime implements RuntimeExtensionInterface
         $pickup = $this->pickups->get($id);
 
         if (null === $pickup) {
-            return 'unbekannt';
+            return null;
         }
 
         return 'ab '.$pickup->getCity();