Fatal error: Uncaught Functional\Exceptions\InvalidArgumentException: Functional\flatten() expects parameter 1 to be array or instance of Traversable, integer given in /var/www/wifi-shop-s00/htdocs/jtlshop/includes/vendor/lstrojny/functional-php/src/Functional/Exceptions/InvalidArgumentException.php:272 Stack trace: #0 /var/www/wifi-shop-s00/htdocs/jtlshop/includes/vendor/lstrojny/functional-php/src/Functional/Exceptions/InvalidArgumentException.php(70): Functional\Exceptions\InvalidArgumentException::assertCollectionAlike(0, 'Traversable', 'Functional\\flat...', 1) #1 /var/www/wifi-shop-s00/htdocs/jtlshop/includes/vendor/lstrojny/functional-php/src/Functional/Flatten.php(26): Functional\Exceptions\InvalidArgumentException::assertCollection(0, 'Functional\\flat...', 1) #2 /var/www/wifi-shop-s00/htdocs/jtlshop/includes/src/Link/LinkGroup.php(136): Functional\flatten(0) #3 /var/www/wifi-shop-s00/htdocs/jtlshop/includes/src/Link/LinkGroupList.php(200): JTL\Link\LinkGroup->map(Array) #4 /var/www/wifi-shop-s00/htdocs/jtlshop/i in /var/www/wifi-shop-s00/htdocs/jtlshop/includes/vendor/lstrojny/functional-php/src/Functional/Exceptions/InvalidArgumentException.php on line 272