fix: properly assign readonly state to form fields for unavailable services

src/Twig/AppRuntime.php

@@ -61,11 +61,7 @@ class AppRuntime implements RuntimeExtensionInterface
      */
     public function formatServicePrice(float|int|null $price): string
     {
-        if (null === $price) {
-            return '';
-        }
-
-        if (0 === $price || 0.0 === $price) {
+        if (null === $price || 0 === $price || 0.0 === $price) {
             return 'inkl.';
         }