Magento 2 Area code is not set Error after upgrade from 2.0.18 to 2.2.8

Question

After upgrading Magento from 2.0.18 to 2.2.8 , lots of report generating in the var/report folder, And below is the exception message. Can anyone help me to fix this issue. Thanks in Advance.

a:4:{i:0;s:20:"Area code is not set";i:1;s:3600:"#1 Magento\Customer\Model\Plugin\CustomerNotification->beforeDispatch(&Magento\Banner\Controller\Ajax\Load\Interceptor#00000000333e0e670000000012966f05#, &Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:121]
#2 Magento\Banner\Controller\Ajax\Load\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:153]
#3 Magento\Banner\Controller\Ajax\Load\Interceptor->___callPlugins('dispatch', array(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#), array(array('customerNotifica...', 'designLoader', 'storeCheck'))) called at [generated/code/Magento/Banner/Controller/Ajax/Load/Interceptor.php:26]
#4 Magento\Banner\Controller\Ajax\Load\Interceptor->dispatch(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/App/FrontController.php:55]
#5 Magento\Framework\App\FrontController->dispatch(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:58]
#6 Magento\Framework\App\FrontController\Interceptor->___callParent('dispatch', array(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#)) called at [vendor/magento/framework/Interception/Interceptor.php:138]
#7 Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/module-store/App/FrontController/Plugin/RequestPreprocessor.php:94]
#8 Magento\Store\App\FrontController\Plugin\RequestPreprocessor->aroundDispatch(&Magento\Framework\App\FrontController\Interceptor#00000000333e0cbc0000000012966f05#, &Closure#00000000333e0cbb0000000012966f05#, &Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:135]
#9 Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/module-page-cache/Model/App/FrontController/BuiltinPlugin.php:69]
#10 Magento\PageCache\Model\App\FrontController\BuiltinPlugin->aroundDispatch(&Magento\Framework\App\FrontController\Interceptor#00000000333e0cbc0000000012966f05#, &Closure#00000000333e0cbb0000000012966f05#, &Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:135]
#11 Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/Interception/Interceptor.php:153]
#12 Magento\Framework\App\FrontController\Interceptor->___callPlugins('dispatch', array(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#), NULL) called at [generated/code/Magento/Framework/App/FrontController/Interceptor.php:26]
#13 Magento\Framework\App\FrontController\Interceptor->dispatch(&Magento\Framework\App\Request\Http#00000000333e0dcd0000000012966f05#) called at [vendor/magento/framework/App/Http.php:136]
#14 Magento\Framework\App\Http->launch() called at [vendor/magento/framework/App/Bootstrap.php:257]
#15 Magento\Framework\App\Bootstrap->run(&Magento\Framework\App\Http\Interceptor#00000000333e0d290000000012966f05#) called at [pub/index.php:37]
";s:3:"url";s:47:"/en/banner/ajax/load/?sections=&_=1560427245352";s:11:"script_name";s:10:"/index.php";}