Merge commit 'refs/pull/922/head' of https://github.com/magento/magento2 into MAGETWO-32969-Empty-System-Message

Conflicts:
	app/code/Magento/AdminNotification/Controller/Adminhtml/System/Message/ListAction.php

Author: marcozheng

app/code/Magento/AdminNotification/Controller/Adminhtml/System/Message/ListAction.php

@@ -14,6 +14,11 @@ class ListAction extends \Magento\Backend\App\AbstractAction
     public function execute()
     {
         $severity = $this->getRequest()->getParam('severity');
+        $default = [
+            'severity' => $severity,
+            'text' => 'All recent issues have been fixed. '
+                .'Please refresh the screen for an update.',
+        ];
         $messageCollection = $this->_objectManager->get(
             'Magento\AdminNotification\Model\Resource\System\Message\Collection'
         );
@@ -22,10 +27,17 @@ public function execute()
         }
         $result = [];
         foreach ($messageCollection->getItems() as $item) {
-            $result[] = ['severity' => $item->getSeverity(), 'text' => $item->getText()];
+            $result[] = [
+                'severity' => $item->getSeverity(),
+                'text' => $item->getText(),
+            ];
+        }
+        if (empty($result)) {
+            $result[] = $default;
         }
         $this->getResponse()->representJson(
-            $this->_objectManager->get('Magento\Core\Helper\Data')->jsonEncode($result)
+            $this->_objectManager->get('Magento\Core\Helper\Data')
+                ->jsonEncode($result)
         );
     }
 }