After adding custom module on Server. It's giving below error

 Fatal error: Uncaught Error: Call to a member function getId() on null
 in
 /var/www/html/magento/vendor/magento/module-backend/Block/Menu.php:296
 Stack trace: #0
 /var/www/html/magento/vendor/magento/framework/View/Element/AbstractBlock.php(975):
 Magento\Backend\Block\Menu->getCacheKeyInfo() #1
 /var/www/html/magento/vendor/magento/framework/View/Element/AbstractBlock.php(1027):
 Magento\Framework\View\Element\AbstractBlock->getCacheKey() #2
 /var/www/html/magento/vendor/magento/framework/View/Element/AbstractBlock.php(652):
 Magento\Framework\View\Element\AbstractBlock->_loadCache() #3
 /var/www/html/magento/vendor/magento/framework/View/Layout.php(542):
 Magento\Framework\View\Element\AbstractBlock->toHtml() #4
 /var/www/html/magento/vendor/magento/framework/View/Layout.php(518):
 Magento\Framework\View\Layout->_renderBlock('menu') #5
 /var/www/html/magento/var/generation/Magento/Framework/View/Layout/Interceptor.php(206):
 Magento\Framework\View\Layout->renderNonCachedElement('menu') #6
 /var/www/html/magento/vendor/magento/framewo in
 /var/www/html/magento/vendor/magento/module-backend/Block/Menu.php on
 line 296

It's displaying when Session Timeout from Admin