[Users] Folder scroll position at folder entry

[Vilius Panevėžys]

Hi,
I realised something I had not thought about before: the affected
folders all have a filtering rule to move messages to them and a
processing rule to delete messages older than X days. Turns out merely
disabling the processing rule makes the issue no longer reproducible.
Another crucial detail is at least one locked message that would be
deleted.

The following scenario reproduces the issue. Hopefully, not only on my
machine.

0. As mentioned before in this thread, I use ascending message sort by
thread date. This is probably related, so set this globally or on the
test folder. At the very least the expected/actual result would be
inverse of what is described below.
1. Create a folder.
2. Copy over one thousand messages. One thousand is not a magic
threshold at which the issue starts happening, but a greater number of
messages seems to increase the frequency at which the issue happens.
One of the folders that suffers from this issue has a little over 100
messages but the issue happens only occasionally. My current test folder
has 1139 messages, which is enough to consistently reproduce the issue.
3. Lock at least one message.
4. Set a processing rule `age_greater X delete`. Choose X such that the
locked message is older than X days (i.e. would be deleted had it not
been locked), but the folder would still have over 1000 messages after
messages older than X are deleted on the next folder entry.
5. Select the last message in the folder.
6. Click on Inbox.
7. Click on the test folder.

Repeat steps 6. and 7. as much as your patience allows. You should get
get the message list view positioned at the top (instead of at the
bottom with the selected message visible) around 80-90%.

I hope other people can reproduce and this bug can be squashed at last!