Move tab replacement logic for next-message-on-delete into the
callback. This also moves the Invalidate() call into the callback, and
should make imap deletion UI work more reliably - there is a race
condition between the worker and the UI in displaying deleted messages.
This should resolve the race condition, and also only remove the MsgView
tab if the message is actually deleted.
Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>