[Users] User changes to message view size do not persist if program is terminated when message view is hidden

[Dustin Miller]

I'm facing a problem that I filed as a bug, but which is now closed as
'WORKSFORME' (i.e. developer not able to reproduce it). (Bug 4521:
https://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=4521).
My system is Linux (Linux Mint 20 XFCE) and I'm using Claws 4.0.0. I'm
curious as to whether anyone else is able to reproduce this, and/or
whether anyone has any idea why this might show up on one system and
not another? Here are the steps to reproduce:

1. Use the 'Standard' layout from 'View - Layout' in the menu. Show the
message view and adjust its size until there are six messages visible
in the message list. Hide the message view.

2. Terminate the Claws Mail program; then start it again.

3. Show the message view.

Actual Result: The message view takes up a larger amount of space such
that only about 2.5 messages are visible in the message list.

Expected Result: There would still be six messages visible in the
message list.

Note that the expected result is how 3.18.0 (gtk2) currently works, in
case that is a helpful reference.

Depending on how often one opens and closes Claws, this bug results in
needing to do a lot of redundant resizing of the message view area
unless one is okay with the default. Based on my use case, I've kept
the priority of this bug at 'Normal', although I do realize that other
use cases would indicate a 'Trivial' or 'Enhancement' priority.