Custom facets throw exception

[mediaessenz]

To reproduce:

Add a custom facet like descripted in the description and register them in a tca configuration
with new \Vendor\MyExt\Facets\MyCustomFacet(),

Add a vidi-frontend-plugin and choose the table with the custom facet.
Watch the PHP Warnings messages inside the backend:

Core: Error handler (BE): PHP Warning: Illegal offset type in /app/public/typo3conf/ext/vidi/Classes/Tca/GridService.php line 188
PHP Warning

Core: Error handler (BE): PHP Warning: Illegal offset type in isset or empty in /app/public/typo3conf/ext/vidi/Classes/Tca/TableService.php line 335
PHP Warning

Core: Error handler (BE): PHP Warning: Illegal offset type in /app/public/typo3conf/ext/vidi/Classes/Tca/GridService.php line 385