Mail folder stays bold with mails all seen

If you read all the emails contained in a folder (other than the INBOX) the folder remains highlighted in bold. Only after a logout/login does it return to normal.

Steps to reproduce:

• create a folder (subfolder or root folder, which is not inbox)
• insert emails to read
• logout/login
• go to the folder, read those mails

Expected behaviour:

• the number disappears and the folder is not bold

Actual behaviour:

• the number disappears but the folder remains in bold

Thanks to federico.ballarini (Ticket ref. #131412)