Use RemoveAllWidgets in RemovedFromManager for robust cleanup

Replace individual RemoveWidget calls with RemoveAllWidgets(false, false)
in generated RemovedFromManager to ensure all child widgets are properly
removed from the container's mWidgets list. This works together with
the existing RemoveAllWidgets in the destructor to prevent
WidgetContainer assertion failure (mWidgets must be empty in destructor).

Author: StackAndPointer

core/code_generator.py

@@ -376,12 +376,7 @@ def generate_cpp_for_interface(self, iface: Interface, project: Project) -> str:
         cpp += "}\n\n"
 
         cpp += f"void {s.class_name}::RemovedFromManager(WidgetManager* theWidgetManager)\n{{\n"
-        for wid_id in iface.root_widget_ids:
-            wid = iface.widgets.get(wid_id)
-            if wid:
-                var_name = self._get_var_name(wid)
-                if self._is_widget_type(wid.class_name):
-                    cpp += f"    RemoveWidget({var_name});\n"
+        cpp += "    RemoveAllWidgets(false, false);\n"
         cpp += f"    {base_class_call}::RemovedFromManager(theWidgetManager);\n}}\n\n"
 
         for listener in listeners: