FIX fo rissue #15510 - First PDF download / export after login

Author: phoenix128

app/code/Magento/Backend/App/AbstractAction.php

@@ -217,6 +217,7 @@ public function dispatch(\Magento\Framework\App\RequestInterface $request)
             $this->_view->loadLayout(['default', 'adminhtml_denied'], true, true, false);
             $this->_view->renderLayout();
             $this->_request->setDispatched(true);
+
             return $this->_response;
         }
 
@@ -226,6 +227,11 @@ public function dispatch(\Magento\Framework\App\RequestInterface $request)
 
         $this->_processLocaleSettings();
 
+        // Need to preload isFirstPageAfterLogin (see https://github.com/magento/magento2/issues/15510)
+        if ($this->_auth->isLoggedIn()) {
+            $this->_auth->getAuthStorage()->isFirstPageAfterLogin();
+        }
+
         return parent::dispatch($request);
     }