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(1608): HookRegistry::call('Templates::Arti...', Array) #5 /var/www/html/cache/t_compile/93b4f13326abf2c920de729fdcdace1580d9bcb7^addd65021fadf964339ab08cd1aa93ba59b14e9c_0.app.frontendobjectsarticle_details.tpl.php(602): 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_6946d0df8d4d70_66637668(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_template.php(386): Smarty_Internal_Template->render() #10 /var/www/html/cache/t_compile/93b4f13326abf2c920de729fdcdace1580d9bcb7^1c372c95cd85572e0fbc9a53d0323a0b229cfc78_0.app.frontendpagesarticle.tpl.php(31): Smarty_Internal_Template->_subTemplateRender('app:frontend/ob...', NULL, '93b4f13326abf2c...', 0, 3600, Array, 0, false) #11 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_6946d0df8531d4_66205400(Object(Smarty_Internal_Template)) #12 /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)) #13 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(217): Smarty_Template_Compiled->render(Object(Smarty_Internal_Template)) #14 /var/www/html/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(238): Smarty_Internal_Template->render(false, 1) #15 /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, '93b4f13326abf2c...', NULL, 1) #16 /var/www/html/lib/pkp/classes/template/PKPTemplateManager.inc.php(1271): Smarty_Internal_TemplateBase->display('frontend/pages/...', NULL, '93b4f13326abf2c...', NULL) #17 /var/www/html/pages/article/ArticleHandler.inc.php(320): PKPTemplateManager->display('frontend/pages/...') #18 /var/www/html/lib/pkp/classes/core/PKPRouter.inc.php(397): ArticleHandler->view(Array, Object(Request)) #19 /var/www/html/lib/pkp/classes/core/PKPPageRouter.inc.php(246): PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(Request), Array, false) #20 /var/www/html/lib/pkp/classes/core/Dispatcher.inc.php(144): PKPPageRouter->route(Object(Request)) #21 /var/www/html/lib/pkp/classes/core/PKPApplication.inc.php(360): Dispatcher->dispatch(Object(Request)) #22 /var/www/html/index.php(68): PKPApplication->execute() #23 {main} thrown in /var/www/html/classes/issue/IssueAction.inc.php on line 29