Fatal error: Uncaught Error: Call to a member function getChildHtml() on null in /home/esecureh/public_html/magdemo/vendor/magento/module-newsletter/view/adminhtml/templates/problem/list.phtml:9 Stack trace: #0 {main} thrown in /home/esecureh/public_html/magdemo/vendor/magento/module-newsletter/view/adminhtml/templates/problem/list.phtml on line 9