fix: prevent null reference errors

src/Controller/Api/TravelController.php

@@ -46,6 +46,10 @@ class TravelController extends AbstractController
     {
         $travel = $this->loadCached($travelId, $hotelId);
 
+        if (null === $travel) {
+            return new JsonResponse(['message' => 'Not found'], Response::HTTP_NOT_FOUND);
+        }
+
         return $this->json($travel, Response::HTTP_OK, [], ['groups' => ['api:list', 'api:single']]);
     }
 
@@ -68,6 +72,10 @@ class TravelController extends AbstractController
 
         $travel = $this->loadCached($travelId, $hotelId);
 
+        if (null === $travel) {
+            return new JsonResponse(['message' => 'Not found'], Response::HTTP_NOT_FOUND);
+        }
+
         return $this->json($travel, Response::HTTP_OK, [], ['groups' => ['api:list', 'api:single']]);
     }
 
@@ -82,7 +90,7 @@ class TravelController extends AbstractController
                 $travel = $this->travelXmlLoader->loadById($travelId, $hotelId);
 
                 if (null === $travel) {
-                    return new JsonResponse(['message' => 'Not found'], Response::HTTP_NOT_FOUND);
+                    return null;
                 }
 
                 $this->pickupXmlLoader->patchPickupsDetails($travel);