[FIX] Node initialization logic for non-dynamic values.

lib/src/form/src/controller.dart

@@ -74,38 +74,37 @@ class AstromicFormController {
     if (_nodes.containsKey(id)) {
       final existingNode = _nodes[id]!;
 
-      // Check if the existing node is already the correct type
       if (existingNode is AstromicFieldNode<T>) {
         return existingNode;
       }
 
-      // If it's a type mismatch (likely <dynamic>), we must migrate it.
-      // We create a new node of the correct type using the existing value.
+      // Determine a safe value for the replacement node
+      T? migratedValue;
+
+      // 1. Try to cast existing value, but handle nulls
+      if (existingNode.value != null) {
+        migratedValue = existingNode.value as T;
+      } else {
+        // 2. Fallback to initialValue or type-specific defaults
+        migratedValue = initialValue ?? _getDefaultValueForType<T>();
+      }
+
       final replacementNode = AstromicFieldNode<T>(
-        existingNode.value as T,
+        migratedValue as T, // Should be safe now
         formatter: (v) => v?.toString() ?? '',
         parser: (v) => (T == String ? v : null) as T?,
       );
 
-      // Transfer validators if they exist
       replacementNode.validators = existingNode.validators;
-
       _nodes[id] = replacementNode;
       return replacementNode;
     }
 
-    // Fallback for new nodes (keep your existing lazy-init logic here)
-    T? defaultValue = initialValue;
-    if (defaultValue == null) {
-      if (T == String)
-        defaultValue = '' as T;
-      else if (T == bool)
-        defaultValue = false as T;
-      else if (T == int) defaultValue = 0 as T;
-    }
+    // Fallback for brand-new nodes
+    final T startValue = initialValue ?? _getDefaultValueForType<T>() as T;
 
     final newNode = AstromicFieldNode<T>(
-      defaultValue as T,
+      startValue,
       formatter: (v) => v?.toString() ?? '',
       parser: (v) => (T == String ? v : null) as T?,
     );
@@ -114,7 +113,13 @@ class AstromicFormController {
     return newNode;
   }
 
-  Type _typeOf<T>() => T;
+  /// Helper to ensure we never pass a null to a non-nullable Node constructor
+  T? _getDefaultValueForType<T>() {
+    if (T == String) return '' as T;
+    if (T == bool) return false as T;
+    if (T == int) return 0 as T;
+    return null;
+  }
 
   bool _isNullable<T>() => null is T;