"Unknown error" when replying to deleted comment via Workbox

Step to reproduce:

1. Create a new page as User B
2. Leave a comment as User A.
3. Open the page as User B and delete the comment by User A
4. Open Workbox as User B
5. Reply to the deleted comment as User B

Expected Behavior

Any proper indicator to notify user that comment has been deleted

Actual Behavior

"Unknow error" shown