### 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
if (theme == p_theme) {
		return;
	}
	theme = p_theme;
	theme_type_editor->set_edited_theme(p_theme);
	theme_edit_dialog->set_edited_theme(p_theme);
	for (int i = 0; i < preview_tabs_content->get_child_count(); i++) {
		ThemeEditorPreview *preview_tab = Object::cast_to<ThemeEditorPreview>(preview_tabs_content->get_child(i));
		if (!preview_tab) {
			continue;
		}
		preview_tab->set_preview_theme(p_theme);
	}
	if (theme.is_valid()) {
		theme_name->set_text(TTR("Theme:") + " " + theme->get_path().get_file());
	}
}
Ref<Theme> ThemeEditor::get_edited_theme() {
	return theme;
}
void ThemeEditor::_theme_save_button_cbk(bool p_save_as) {
	ERR_FAIL_COND_MSG(theme.is_null(), "Invalid state of the Theme Editor; the Theme resource is missing.");
	if (p_save_as) {
		EditorNode::get_singleton()->save_resource_as(theme);
	} else {
		EditorNode::get_singleton()->save_resource(theme);
	}
}
void ThemeEditor::_theme_edit_button_cbk() {