Fatal error: Uncaught TypeError: Argument 1 passed to Sokil\IsoCodes\Database\Countries::getByAlpha2() must be of the type string, null given, called in /home/journals/public_html/pages/search/SearchHandler.inc.php on line 272 and defined in /home/journals/public_html/lib/pkp/lib/vendor/sokil/php-isocodes/src/Database/Countries.php:42 Stack trace: #0 /home/journals/public_html/pages/search/SearchHandler.inc.php(272): Sokil\IsoCodes\Database\Countries->getByAlpha2(NULL) #1 /home/journals/public_html/lib/pkp/classes/core/PKPRouter.inc.php(391): SearchHandler->authors(Array, Object(Request)) #2 /home/journals/public_html/lib/pkp/classes/core/PKPPageRouter.inc.php(231): PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(Request), Array, false) #3 /home/journals/public_html/lib/pkp/classes/core/Dispatcher.inc.php(143): PKPPageRouter->route(Object(Request)) #4 /home/journals/public_html/lib/pkp/classes/core/PKPApplication.inc.php(278): Dispatcher->dispatch(Object(Request)) #5 /home/journals/public_html/index.php(68): P in /home/journals/public_html/lib/pkp/lib/vendor/sokil/php-isocodes/src/Database/Countries.php on line 42