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Fatal error: Uncaught TypeError: Argument 1 passed to Sokil\IsoCodes\Database\Countries::getByAlpha2() must be of the type string, null given, called in C:\www\pages\search\SearchHandler.inc.php on line 272 and defined in C:\www\lib\pkp\lib\vendor\sokil\php-isocodes\src\Database\Countries.php:42 Stack trace: #0 C:\www\pages\search\SearchHandler.inc.php(272): Sokil\IsoCodes\Database\Countries->getByAlpha2(NULL) #1 C:\www\lib\pkp\classes\core\PKPRouter.inc.php(391): SearchHandler->authors(Array, Object(Request)) #2 C:\www\lib\pkp\classes\core\PKPPageRouter.inc.php(231): PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(Request), Array, false) #3 C:\www\lib\pkp\classes\core\Dispatcher.inc.php(143): PKPPageRouter->route(Object(Request)) #4 C:\www\lib\pkp\classes\core\PKPApplication.inc.php(279): Dispatcher->dispatch(Object(Request)) #5 C:\www\index.php(68): PKPApplication->execute() #6 {main} th