[FIX] Field Groups hydration

lib/src/form/src/controller.dart

@@ -145,15 +145,22 @@ 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}';
 
     def.schema.forEach((fieldName, config) {
       final nodeKey = '${groupId}_${fieldName}_$newUuid';
-      final startVal = initialData?[fieldName] ?? config.initialValue;
+
+      // 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);
     });
 
-    for (var sub in def.subGroups) {
+    // Handle subGroups safely
+    final subGroups = def.subGroups;
+    for (var sub in subGroups) {
       final subKey = '${groupId}_${sub}_${newUuid}_manifest';
       _nodes[subKey] = AstromicFieldNode<List<String>>(
         [],