Update message counter in msglist when the filter is changed (either set or
cleared in the msgstore).
When we apply a filter, we change the number of uids in the message
store. This can unintentionally trigger the storeUpdate() function of
the msglist which checks the number of uids for new messages and
advances the pointer by the difference in the number of messages. This
can be avoided when we update the message counter upon changing the
filter.
Fixes: https://todo.sr.ht/~rjarry/aerc/23
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>