fix: allow hotel-less travel data

addresses #869ckkwh7

src/BusProNet/XmlLoader/HotelLoader.php

@@ -91,6 +91,12 @@ class HotelLoader extends AbstractLoader
     public function patchHotelDetails(Travel $travel): void
     {
         $hotelId = $travel->hotelId;
+        if (null === $hotelId) {
+            $travel->hotel = null;
+
+            return;
+        }
+
         try {
             $hotel = $this->loadById($hotelId);
             $travel->hotel = $hotel;