TypeError at registerIcon

[pfaffenrodt]

Fluidcontent is trying to register NULL as icon.

This Error disappear after flushing cache. But it recurring after some times. I dont really know how to reproduce it. Happend again after composer install.

Argument 3 passed to TYPO3\CMS\Core\Imaging\IconRegistry::registerIcon() must be of the type array, boolean given, called in
\web\typo3conf\ext\fluidcontent\Classes\Service\ConfigurationService.php on line 165

TypeError thrown in file
vendor\typo3\cms\typo3\sysext\core\Classes\Imaging\IconRegistry.php in line 2854.
TYPO3\CMS\Core\Imaging\IconRegistry::registerIcon(NULL, NULL, boolean)