No feedback message when menu item is created with duplicate name

Steps to reproduce
1) Go to the channel manager, edit a channel and open the menu editor
2) Create a menu item named 'Contact'
3) Create another menu item with label 'Contact'
4) Try to navigate to another menu
5) Expected: Message or hint 'The menu item 'Content' already exists as a top menu item'
6) Actual: The Label has a red border but no indication what is wrong. No hint is shown

In 7.9 a message was displayed 'The menu item 'Content' already exists as a top menu item' . When the label field is empty you do see a message ' Label is required', expecting either a message like 7.9 or a hint like the empty-field hint