neon: cleanup SortBoxBuilder

packages/neon/neon/lib/src/utils/sort_box_builder.dart

@@ -17,14 +17,21 @@ class SortBoxBuilder<T extends Enum, R> extends StatelessWidget {
   final Widget Function(BuildContext, List<R>?) builder;
 
   @override
-  Widget build(final BuildContext context) => OptionBuilder<T>(
+  Widget build(final BuildContext context) {
+    if (input == null || (input?.isEmpty ?? false)) {
+      return builder(context, null);
+    }
+
+    return OptionBuilder<T>(
       option: sortPropertyOption,
       builder: (final context, final property) => OptionBuilder<SortBoxOrder>(
         option: sortBoxOrderOption,
-          builder: (final context, final order) => builder(
-            context,
-            input == null ? null : sortBox.sort(input!, Box(property, order)),
-          ),
+        builder: (final context, final order) {
+          final box = Box(property, order);
+
+          return builder(context, sortBox.sort(input!, box));
+        },
       ),
     );
   }
+}