### 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
names.clear();
		ThemeDB::get_singleton()->get_default_theme()->get_constant_list(default_type, &names);
		for (const StringName &E : names) {
			if (!new_snapshot->has_constant(E, edited_type)) {
				new_snapshot->set_constant(E, edited_type, ThemeDB::get_singleton()->get_default_theme()->get_constant(E, edited_type));
			}
		}
	}
	updating = false;
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Override All Default Theme Items"));
	ur->add_do_method(*edited_theme, "merge_with", new_snapshot);
	ur->add_undo_method(*edited_theme, "clear");
	ur->add_undo_method(*edited_theme, "merge_with", old_snapshot);
	ur->add_do_method(this, "_update_type_items");
	ur->add_undo_method(this, "_update_type_items");
	ur->commit_action();
}
void ThemeTypeEditor::_item_add_cbk(int p_data_type, Control *p_control) {
	LineEdit *le = Object::cast_to<LineEdit>(p_control);
	if (le->get_text().strip_edges().is_empty()) {
		return;
	}
	String item_name = le->get_text().strip_edges();
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Add Theme Item"));
	switch (p_data_type) {
		case Theme::DATA_TYPE_COLOR: {
			ur->add_do_method(*edited_theme, "set_color", item_name, edited_type, Color());
			ur->add_undo_method(*edited_theme, "clear_color", item_name, edited_type);