Fatal error: Uncaught Error: Call to a member function getJournalId() on null in /var/www/php7/ejournal/web/classes/issue/IssueAction.inc.php:31 Stack trace: #0 /var/www/php7/ejournal/web/classes/search/ArticleSearch.inc.php(273): IssueAction->subscriptionRequired(NULL, Object(Journal)) #1 /var/www/php7/ejournal/web/plugins/generic/recommendByAuthor/RecommendByAuthorPlugin.inc.php(142): ArticleSearch->formatResults(Array) #2 /var/www/php7/ejournal/web/lib/pkp/classes/plugins/HookRegistry.inc.php(107): RecommendByAuthorPlugin->callbackTemplateArticlePageFooter('Templates::Arti...', Array) #3 /var/www/php7/ejournal/web/lib/pkp/classes/template/PKPTemplateManager.inc.php(1578): HookRegistry::call('Templates::Arti...', Array) #4 /var/www/php7/ejournal/web/cache/t_compile/42362804174f266c598cdb32c3208fc745b92101^1c372c95cd85572e0fbc9a53d0323a0b229cfc78_0.app.frontendpagesarticle.tpl.php(43): PKPTemplateManager->smartyCallHook(Array, Object(Smarty_Internal_Template)) #5 /var/www/php7/ejournal/web/lib/pkp/lib/vendor/smarty/smart in /var/www/php7/ejournal/web/classes/issue/IssueAction.inc.php on line 31