[FIX] mail: fixed replying to the first message in Inbox that was crashing
[FIX] mail: fixed reply button in mail_mail form view, should reply
to a mail.message, not a mail.mail.
[FIX] mail: in some cases tracking is called
without the context (some workflows for example). In that case use the
current user lang when generating the automatic message. This is done
by adding it in the context if not present.