Fatal error: Uncaught TypeError: PKP\core\PKPString::convertStrftimeFormat(): Argument #1 ($format) must be of type string, null given, called in /var/www/ejournal/lib/pkp/classes/template/PKPTemplateManager.php on line 190 and defined in /var/www/ejournal/lib/pkp/classes/core/PKPString.php:559 Stack trace: #0 /var/www/ejournal/lib/pkp/classes/template/PKPTemplateManager.php(190): PKP\core\PKPString::convertStrftimeFormat() #1 /var/www/ejournal/classes/template/TemplateManager.php(40): PKP\template\PKPTemplateManager->initialize() #2 /var/www/ejournal/lib/pkp/classes/template/PKPTemplateManager.php(1442): APP\template\TemplateManager->initialize() #3 /var/www/ejournal/lib/pkp/classes/plugins/Plugin.php(403): PKP\template\PKPTemplateManager::getManager() #4 /var/www/ejournal/lib/pkp/classes/plugins/Plugin.php(137): PKP\plugins\Plugin->_registerTemplateResource() #5 /var/www/ejournal/lib/pkp/classes/plugins/LazyLoadPlugin.php(34): PKP\plugins\Plugin->register() #6 /var/www/ejournal/plugins/generic/recommendByAuthor/RecommendByAuthorPlugin.php(43): PKP\plugins\LazyLoadPlugin->register() #7 /var/www/ejournal/lib/pkp/classes/plugins/PluginRegistry.php(76): APP\plugins\generic\recommendByAuthor\RecommendByAuthorPlugin->register() #8 /var/www/ejournal/lib/pkp/classes/plugins/PluginRegistry.php(121): PKP\plugins\PluginRegistry::register() #9 [internal function]: PKP\plugins\PluginRegistry::PKP\plugins\{closure}() #10 /var/www/ejournal/lib/pkp/classes/plugins/PluginRegistry.php(121): array_walk_recursive() #11 /var/www/ejournal/lib/pkp/classes/core/Dispatcher.php(155): PKP\plugins\PluginRegistry::loadCategory() #12 /var/www/ejournal/lib/pkp/classes/core/PKPApplication.php(395): PKP\core\Dispatcher->dispatch() #13 /var/www/ejournal/index.php(21): PKP\core\PKPApplication->execute() #14 {main} thrown in /var/www/ejournal/lib/pkp/classes/core/PKPString.php on line 559