### Godot version

4.1.1

### System information

linux

### Issue description

[simplescreenrecorder-2023-08-30_15.01.51.webm](https://github.com/godotengine/godot-proposals/assets/71937306/537d92b9-4f98-4fe6-adf4-71297be0471a)

I guess this wasn't the case before since I could save a layout named "2 monitors".

### Steps to reproduce

press space

### Minimal reproduction project

none
ur->add_do_method(*edited_theme, "set_color", p_item_name, p_item_type, Color());
			ur->add_undo_method(*edited_theme, "clear_color", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_CONSTANT:
			ur->add_do_method(*edited_theme, "set_constant", p_item_name, p_item_type, 0);
			ur->add_undo_method(*edited_theme, "clear_constant", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_MAX:
			break; 
	}
	ur->add_do_method(this, "_update_edit_item_tree", edited_item_type);
	ur->add_undo_method(this, "_update_edit_item_tree", edited_item_type);
	ur->commit_action();
}
void ThemeItemEditorDialog::_remove_theme_type(const String &p_theme_type) {
	Ref<Theme> old_snapshot = edited_theme->duplicate();
	Ref<Theme> new_snapshot = edited_theme->duplicate();
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Remove Theme Type"));
	new_snapshot->remove_type(p_theme_type);
	ur->add_do_method(*edited_theme, "clear");
	ur->add_do_method(*edited_theme, "merge_with", new_snapshot);
	
	ur->add_undo_method(*edited_theme, "add_type", p_theme_type);
	ur->add_undo_method(*edited_theme, "merge_with", old_snapshot);
	ur->add_do_method(this, "_update_edit_types");
	ur->add_undo_method(this, "_update_edit_types");
	ur->commit_action();
}
void ThemeItemEditorDialog::_remove_data_type_items(Theme::DataType p_data_type, String p_item_type) {