I'm using QuickCart 6.6 on a local server and getting a fatal error while creating a new language (using the default language) or deleting a language.
The error starts with: Fatal error: Uncaught UnexpectedValueException: DirectoryIterator::__construct(database/pages/,database/pages/)
While creating a language the error also links to line 175 of file "core\lang-admin.php" While deleting a language the error also links to line 211 of file "core\lang-admin.php"
Afterwards the language is added / deleted. So that part does work.