(OJS-3.3.0-13) PHP Fatal error: Uncaught Error: Call to a member function getPublished() on null in

We found this error while checking server logs. I don’t know what is the problem and what is its effect.

We are getting this error for a long time.
We are using PHP 7.4, MYSQL 8.0.

[25-Jan-2023 10:43:35 Asia/Kolkata] PHP Fatal error:  Uncaught Error: Call to a member function getPublished() on null in /EPUB/ojs/cache/t_compile/f9cbad54bc17edf9cd863b38d6dce3361ce3799b^acf1fc671fe3149386beb488bd42d95154e9d6f3_0.app.frontendpagessearchAuthor.php:49
Stack trace:
#0 /EPUB/ojs/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_63b3e394ae5a42_12060158()
#1 /EPUB/ojs/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_compiled.php(114): Smarty_Template_Resource_Base->getRenderedTemplateCode()
#2 /EPUB/ojs/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_template.php(216): Smarty_Template_Compiled->render()
#3 /EPUB/ojs/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(232): Smarty_Internal_Template->render()
#4 /EPUB/ojs/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatebase.php(134): Smarty_Internal_TemplateBase->_execute()
#5 /EPUB/ojs/lib/pkp/classes/template/PKPTemplateManager.inc.php(1187): Smarty_Internal_Template in /EPUB/ojs/cache/t_compile/f9cbad54bc17edf9cd863b38d6dce3361ce3799b^acf1fc671fe3149386beb488bd42d95154e9d6f3_0.app.frontendpagessearchAuthor.php on line 49