chore: fix phpstan errors

src/BusProNet/Model/Booking.php

@@ -220,7 +220,7 @@ class Booking
     public function getInsuranceForParticipant(int $participantIndex): ?Insurance
     {
         foreach ($this->insurances as $insurance) {
-            if (in_array($participantIndex, $insurance->mapping ?? [], true)) {
+            if (in_array($participantIndex, $insurance->mapping, true)) {
                 return $insurance;
             }
         }