[FIX] Field Groups hydration

lib/src/form/src/controller.dart

@@ -148,32 +148,32 @@ class AstromicFormController {
     final def = _groupDefs[groupId];
     if (def == null) throw Exception('Group $groupId not registered.');
 
-    // Use a more robust ID to prevent any possibility of collision on fast clicks
     final newUuid = '${DateTime.now().microsecondsSinceEpoch}_${_nodes.length}';
 
+    // 1. Fields loop (Keep as is)
     def.schema.forEach((fieldName, config) {
       final nodeKey = '${groupId}_${fieldName}_$newUuid';
-
-      // THE FIX: Explicitly check for null initialData before indexing
-      // This prevents the null-pointer crash on Web
       final dynamic startVal = (initialData != null && initialData.containsKey(fieldName)) ? initialData[fieldName] : config.initialValue;
-
       config.register(nodeKey, startVal, _createTypedNode);
     });
 
-    // Handle subGroups safely
-    final subGroups = def.subGroups;
-    for (var sub in subGroups) {
+    // 2. THE FIX: Defensive check for null subGroups
+    final subGroupsList = def.subGroups;
+    if (subGroupsList != null) {
+      for (var sub in subGroupsList) {
         final subKey = '${groupId}_${sub}_${newUuid}_manifest';
         _nodes[subKey] = AstromicFieldNode<List<String>>(
-        [],
+          <String>[],
           formatter: (v) => v.length.toString(),
-        parser: (v) => [],
+          parser: (v) => <String>[],
         );
       }
+    }
 
+    // 3. Update the Parent Manifest
     final manifest = getManifest(groupId, parentUuid);
     manifest.value = [...manifest.value, newUuid];
+
     return newUuid;
   }