Uncaught Typo3 Exception on Saving

Typo3 8.7.26 After filling Data in "Tracking / Cookies" an click save:

Uncaught TYPO3 Exception explode() expects parameter 2 to be string, null given

TypeError thrown in file /www/typo3shared/typo3_src-8.7.26/typo3/sysext/core/Classes/Database/Query/Restriction/FrontendGroupRestriction.php in line 36.

19 explode(",", NULL)

/www/typo3shared/typo3_src-8.7.26/typo3/sysext/core/Classes/Database/Query/Restriction/FrontendGroupRestriction.php: 00034: public function __construct(array $frontendGroupIds = null) 00035: { 00036: $this->frontendGroupIds = $frontendGroupIds === null ? explode(',', $GLOBALS['TSFE']->gr_list) : $frontendGroupIds; 00037: } 00038:

18 TYPO3\CMS\Core\Database\Query\Restriction\FrontendGroupRestriction::__construct()

/www/typo3shared/typo3_src-8.7.26/typo3/sysext/core/Classes/Utility/GeneralUtility.php: 03966: } 03967: // Create new instance and call constructor with parameters 03968: $instance = new finalClassName(...constructorArguments); 03969: // Register new singleton instance 03970: if ($instance instanceof SingletonInterface) {

17 TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance("TYPO3\CMS\Core\Database\Query\Restriction\FrontendGroupRestriction")

/www/typo3shared/typo3_src-8.7.26/typo3/sysext/core/Classes/Database/Query/Restriction/AbstractRestrictionContainer.php: 00099: protected function createRestriction($restrictionClass) 00100: { 00101: return GeneralUtility::makeInstance($restrictionClass); 00102: } 00103: }

16 TYPO3\CMS\Core\Database\Query\Restriction\AbstractRestrictionContainer::createRestriction("TYPO3\CMS\Core\Database\Query\Restriction\FrontendGroupRestriction")

/www/typo3shared/typo3_src-8.7.26/typo3/sysext/core/Classes/Database/Query/Restriction/FrontendRestrictionContainer.php: 00045: { 00046: foreach ($this->defaultRestrictionTypes as $restrictionType) { 00047: $this->add($this->createRestriction($restrictionType)); 00048: } 00049: }