Fix "NestedForm Inherits Values from Parent Form" Bug

[apple-bears]

Related Issue

#4

Updates

Create a dummy model that prevents nested form fields from inheriting
values from the parent form's model. This is necessary because:

1. Form widgets use getLoadValue() which falls back to $this->model when data is falsy (FormWidgetBase line 150)
2. When a nested form field (e.g., "name") doesn't exist in the nested data array, it would otherwise check the parent model and inherit the parent's "name" value
3. The Form widget requires a model instance, so we provide a dummy one that always returns null for attributes

Screenshot

The repeater form doesn't show the page name as shown in the issue.