fix: prevent null pointer exception

src/Twig/AppRuntime.php

@@ -50,8 +50,12 @@ 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';
+        }
+        
         $pickup = $this->pickups->get($id);
 
         if (null === $pickup) {