Fix corrupt undo after making sub-resources unique

editor/inspector_dock.cpp

@@ -186,7 +186,7 @@ void InspectorDock::_menu_option_confirm(int p_option, bool p_confirmed) {
 					}
 				}
 
-				int history_id = EditorUndoRedoManager::get_singleton()->get_history_for_object(current).id;
+				int history_id = EditorUndoRedoManager::get_singleton()->get_history_id_for_object(current);
 				EditorUndoRedoManager::get_singleton()->clear_history(true, history_id);
 
 				EditorNode::get_singleton()->edit_item(current, inspector);