fix: show rental insurance field only when applicable

src/Form/ParticipantType.php

@@ -256,12 +256,14 @@ class ParticipantType extends AbstractType
                 'choices' => $options['selectable_parking'],
             ]);
 
-            // Rental Insurance - single checkbox (always add, JS will show/hide when rentals selected)
-            $form->add('rentalInsurance', ChoiceType::class, [
-                ...$commonChoiceFieldOptions,
-                'label' => 'Leihausrüstungsversicherung',
-                'choices' => $options['selectable_rental_insurance'],
-            ]);
+            // Rental Insurance - single checkbox (only add if available, JS will show/hide when rentals selected)
+            if (0 < count($options['selectable_rental_insurance'])) {
+                $form->add('rentalInsurance', ChoiceType::class, [
+                    ...$commonChoiceFieldOptions,
+                    'label' => false,
+                    'choices' => $options['selectable_rental_insurance'],
+                ]);
+            }
 
             // Transportation
             $transportationChoiceAttributes = function (?Service $service) use ($options) {