Fatal error: Uncaught AssertionError: assert(is_a($issue, 'Issue')) in /var/www/html/classes/issue/IssueAction.inc.php:29 Stack trace: #0 /var/www/html/classes/issue/IssueAction.inc.php(29): assert(false, 'assert(is_a($is...') #1 /var/www/html/classes/search/ArticleSearch.inc.php(273): IssueAction->subscriptionRequired(NULL, Object(Journal)) #2 /var/www/html/plugins/generic/recommendByAuthor/RecommendByAuthorPlugin.inc.php(142): ArticleSearch->formatResults(Array) #3 /var/www/html/lib/pkp/classes/plugins/HookRegistry.inc.php(107): RecommendByAuthorPlugin->callbackTemplateArticlePageFooter('Templates::Arti...', Array) #4 /var/www/html/lib/pkp/classes/template/PKPTemplateManager.inc.php(1581): HookRegistry::call('Templates::Arti...', Array) #5 /var/www/html/cache/t_compile/42362804174f266c598cdb32c3208fc745b92101^1c372c95cd85572e0fbc9a53d0323a0b229cfc78_0.app.frontendpagesarticle.tpl.php(43): PKPTemplateManager->smartyCallHook(Array, Object(Smarty_Internal_Template)) #6 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_68fbbae27db940_62768000(Object(Smarty_Internal_Template)) #7 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_compiled.php(114): Smarty_Template_Resource_Base->getRenderedTemplateCode(Object(Smarty_Internal_Template)) #8 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(217): Smarty_Template_Compiled->render(Object(Smarty_Internal_Template)) #9 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(238): Smarty_Internal_Template->render(false, 1) #10 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(134): Smarty_Internal_TemplateBase->_execute(Object(Smarty_Internal_Template), NULL, '42362804174f266...', NULL, 1) #11 /var/www/html/lib/pkp/classes/template/PKPTemplateManager.inc.php(1250): Smarty_Internal_TemplateBase->display('frontend/pages/...', NULL, '42362804174f266...', NULL) #12 /var/www/html/pages/article/ArticleHandler.inc.php(320): PKPTemplateManager->display('frontend/pages/...') #13 /var/www/html/lib/pkp/classes/core/PKPRouter.inc.php(397): ArticleHandler->view(Array, Object(Request)) #14 /var/www/html/lib/pkp/classes/core/PKPPageRouter.inc.php(246): PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(Request), Array, false) #15 /var/www/html/lib/pkp/classes/core/Dispatcher.inc.php(144): PKPPageRouter->route(Object(Request)) #16 /var/www/html/lib/pkp/classes/core/PKPApplication.inc.php(360): Dispatcher->dispatch(Object(Request)) #17 /var/www/html/index.php(68): PKPApplication->execute() #18 {main} thrown in /var/www/html/classes/issue/IssueAction.inc.php on line 29