TYPO3 Core

When installing a new site package in TYPO 9.4.0 with a data.t3d or data.xml in the Initialisation directory, data does not get imported. When setting it up with helhum's console, an error occurs and when doing it by hand via the Extension Manager, the extension is installed, but the data file is not being imported. I tried it multiple times with new databases. AFAIK this still worked in 9.3.0. I also created a new @data.t3d file in v9.4.0 for testing and used that instead, but same error. This is what the console says:

[ TYPO3\CMS\Core\Error\Exception ]

Warning: reset() expects parameter 1 to be array, null given in 
/mnt/e/xampp/htdocs/tests/test.de/public/typo3/sysext/impexp/Classes/Utility/ImportExportUtility.php line 58