MAGETWO-86484: Fix jumping content on page reload in admin area #12985

 - Merge Pull Request magento/magento2#12985 from avoelkl/magento2:feature/no-admin-page-jumps
 - Merged commits:
   1. c3943ec2

app/design/adminhtml/Magento/backend/web/css/source/_structure.less

@@ -36,6 +36,7 @@ body {
 //  ToDo UI: should be moved to messages
 .notices-wrapper {
     margin: 0 3rem;
+    min-height: 5rem;
     .messages {
         margin-bottom: 0;
     }