Undefined array key warning if extension is installed and not properly set up

I installed sgalinski-cookie-optin with composer on my local docker machine. If no Extension configuration is done after install, the Arrey key $GLOBALS['TYPO3_CONF_VARS']['EXTENSIONS']['sg_cookie_optin'] does not exists. I use TYPO3 11.5.24 and PHP 8.1. I configuration set once then is ok. For the moment I patched line 62 in sg_cookie_optin/Classes/Service/ExtensionSettingsService.php

$configuration = $GLOBALS['TYPO3_CONF_VARS']['EXTENSIONS']['sg_cookie_optin'] ?? '';

That helps.