Nullable types must be explicit

Not sure what the test failures are caused by, but this applies cleanly and resolves the issue for me.

I am getting the same.
Running drush cr on my Drupal site with PHP 8.4.3 produces deprecation warnings related to implicitly nullable parameters in the config_split module.
Steps to Reproduce:
1. Install the latest version of config_split.
2. Use PHP 8.4.3.
3. Run drush cr.
Actual Result:
Deprecation warnings appear in the logs:

PHP Deprecated:  Drupal\config_split\EventSubscriber\SplitImportExportSubscriber::getDefaultPrioritySplitConfigs(): Implicitly marking parameter $storage as nullable is deprecated, the explicit nullable type must be used instead in /web/modules/contrib/config_split/src/EventSubscriber/SplitImportExportSubscriber.php on line 123

PHP Deprecated:  Drupal\config_split\Form\ConfigImportFormTrait::launchImport(): Implicitly marking parameter $override as nullable is deprecated, the explicit nullable type must be used instead in /web/modules/contrib/config_split/src/Form/ConfigImportFormTrait.php on line 203

Expected Result:
No deprecation warnings should appear when running drush cr.

I believe all the changes in the MR are now applied in the latest version. I removed the patch, and don't see any errors when running drush commands at least (how I noticed the issue before I added the patch). I assume the issue can be marked accordingly