fix: enable bookings without ski passes

tests/Form/Service/ParticipantFieldOptionsProviderSkiPassAvailabilityTest.php

@@ -134,6 +134,17 @@ class ParticipantFieldOptionsProviderSkiPassAvailabilityTest extends TestCase
         }
     }
 
+    public function testTravelWithoutSkiPassesRendersNoField(): void
+    {
+        $bookingDto = $this->createBookingDto([]);
+
+        $this->assertSame(
+            [],
+            $this->provider->getFieldOptions('skiPass', $bookingDto, 0),
+            'The field has to be absent entirely, not rendered with an empty choice list'
+        );
+    }
+
     /** @return int[] */
     private function getSkiPassChoiceIds(BookingDto $bookingDto): array
     {