Omeka S encountered an error

Error
Call to a member function valueRepresentation() on null

Details:

Error: Call to a member function valueRepresentation() on null in /var/www/vhosts/mct.barnard.edu/httpdocs/application/src/DataType/Resource/AbstractResource.php:81
Stack trace:
#0 /var/www/vhosts/mct.barnard.edu/httpdocs/application/src/Api/Representation/ValueRepresentation.php(67): Omeka\DataType\Resource\AbstractResource->getJsonLd()
#1 [internal function]: Omeka\Api\Representation\ValueRepresentation->jsonSerialize()
#2 /var/www/vhosts/mct.barnard.edu/httpdocs/application/src/Api/Representation/AbstractResourceRepresentation.php(290): json_encode()
#3 /var/www/vhosts/mct.barnard.edu/httpdocs/application/Module.php(152): Omeka\Api\Representation\AbstractResourceRepresentation->embeddedJsonLd()
#4 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-eventmanager/src/EventManager.php(322): Omeka\Module->Omeka\{closure}()
#5 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-eventmanager/src/EventManager.php(171): Zend\EventManager\EventManager->triggerListeners()
#6 /var/www/vhosts/mct.barnard.edu/httpdocs/application/src/View/Helper/Trigger.php(61): Zend\EventManager\EventManager->triggerEvent()
#7 [internal function]: Omeka\View\Helper\Trigger->__invoke()
#8 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-view/src/Renderer/PhpRenderer.php(397): call_user_func_array()
#9 /var/www/vhosts/mct.barnard.edu/httpdocs/themes/view-from-ginling/view/omeka/site/item/show.phtml(14): Zend\View\Renderer\PhpRenderer->__call()
#10 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-view/src/Renderer/PhpRenderer.php(506): include('/var/www/vhosts...')
#11 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-view/src/View.php(207): Zend\View\Renderer\PhpRenderer->render()
#12 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-view/src/View.php(236): Zend\View\View->render()
#13 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-view/src/View.php(200): Zend\View\View->renderChildren()
#14 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-mvc/src/View/Http/DefaultRenderingStrategy.php(105): Zend\View\View->render()
#15 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-eventmanager/src/EventManager.php(322): Zend\Mvc\View\Http\DefaultRenderingStrategy->render()
#16 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-eventmanager/src/EventManager.php(171): Zend\EventManager\EventManager->triggerListeners()
#17 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-mvc/src/Application.php(367): Zend\EventManager\EventManager->triggerEvent()
#18 /var/www/vhosts/mct.barnard.edu/httpdocs/vendor/zendframework/zend-mvc/src/Application.php(348): Zend\Mvc\Application->completeRequest()
#19 /var/www/vhosts/mct.barnard.edu/httpdocs/index.php(21): Zend\Mvc\Application->run()
#20 {main}