Fatal error: Uncaught Error: Call to a member function getData() on null in /var/www/html/ojs-3.4.0-8/plugins/generic/recommendBySimilarity/RecommendBySimilarityPlugin.php:96 Stack trace: #0 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Collections/LazyCollection.php(789): APP\plugins\generic\recommendBySimilarity\RecommendBySimilarityPlugin->APP\plugins\generic\recommendBySimilarity\{closure}() #1 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Collections/LazyCollection.php(1545): Illuminate\Support\LazyCollection->Illuminate\Support\{closure}() #2 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Collections/LazyCollection.php(788): Illuminate\Support\LazyCollection->Illuminate\Support\{closure}() #3 [internal function]: Illuminate\Support\LazyCollection->Illuminate\Support\{closure}() #4 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Collections/LazyCollection.php(105): iterator_to_array() #5 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Collections/Traits/EnumeratesValues.php(847): Illuminate\Support\LazyCollection->all() #6 /var/www/html/ojs-3.4.0-8/plugins/generic/recommendBySimilarity/RecommendBySimilarityPlugin.php(98): Illuminate\Support\LazyCollection->toArray() #7 /var/www/html/ojs-3.4.0-8/plugins/generic/recommendBySimilarity/RecommendBySimilarityPlugin.php(46): APP\plugins\generic\recommendBySimilarity\RecommendBySimilarityPlugin->buildTemplate() #8 [internal function]: APP\plugins\generic\recommendBySimilarity\RecommendBySimilarityPlugin->APP\plugins\generic\recommendBySimilarity\{closure}() #9 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/plugins/Hook.php(139): call_user_func_array() #10 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/plugins/Hook.php(113): PKP\plugins\Hook::run() #11 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/template/PKPTemplateManager.php(1787): PKP\plugins\Hook::call() #12 /var/www/html/ojs-3.4.0-8/cache/t_compile/d7f9b89232beccee9968dd59184e678fb8b9042e^addd65021fadf964339ab08cd1aa93ba59b14e9c_0.app.frontendobjectsarticle_details.tpl.php(561): PKP\template\PKPTemplateManager->smartyCallHook() #13 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_68a9eb58c3c3b6_74531062() #14 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_compiled.php(114): Smarty_Template_Resource_Base->getRenderedTemplateCode() #15 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(217): Smarty_Template_Compiled->render() #16 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(386): Smarty_Internal_Template->render() #17 /var/www/html/ojs-3.4.0-8/cache/t_compile/d7f9b89232beccee9968dd59184e678fb8b9042e^1c372c95cd85572e0fbc9a53d0323a0b229cfc78_0.app.frontendpagesarticle.tpl.php(44): Smarty_Internal_Template->_subTemplateRender() #18 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_68a9eb58af0500_35042095() #19 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_compiled.php(114): Smarty_Template_Resource_Base->getRenderedTemplateCode() #20 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(217): Smarty_Template_Compiled->render() #21 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(238): Smarty_Internal_Template->render() #22 /var/www/html/ojs-3.4.0-8/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(134): Smarty_Internal_TemplateBase->_execute() #23 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/template/PKPTemplateManager.php(1372): Smarty_Internal_TemplateBase->display() #24 /var/www/html/ojs-3.4.0-8/pages/article/ArticleHandler.php(355): PKP\template\PKPTemplateManager->display() #25 [internal function]: APP\pages\article\ArticleHandler->view() #26 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/core/PKPRouter.php(334): call_user_func() #27 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/core/PKPPageRouter.php(278): PKP\core\PKPRouter->_authorizeInitializeAndCallRequest() #28 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/core/Dispatcher.php(165): PKP\core\PKPPageRouter->route() #29 /var/www/html/ojs-3.4.0-8/lib/pkp/classes/core/PKPApplication.php(395): PKP\core\Dispatcher->dispatch() #30 /var/www/html/ojs-3.4.0-8/index.php(21): PKP\core\PKPApplication->execute() #31 {main} thrown in /var/www/html/ojs-3.4.0-8/plugins/generic/recommendBySimilarity/RecommendBySimilarityPlugin.php on line 96