Sorting by state loses sorting by date in some cases

When sorting by state, secondary sorting by date is lost in some cases.
In particular it happens with emails that have a reply or a forward.

Steps to reproduce:

• set sorting by date
• prepare some emails with similar dates
• reply and forward some of these emails
• leave some emails unread
• change order by state

 Expected behaviour:

• the e-mails to be read are all sorted at the top and the descending date is used as secondary order

Actual behaviour:

• read emails that have been answered or forwarded are ordered before others to be read (see example image)

Tanks to Matteo Magi (Ref. #99312)