[MlMt] Odd behavior when switching mailbox to view

[Eric Sharakan]

Hi, when switching to a different mailbox, the pane with the one-line preview of configured headers often ends up in a random position, instead of always showing the most recent messages (which I have configured to be at the bottom, using the "Thread Arcs" layout).

This seemed to start right around r5909, the build in which Benny resolved an issue with saving/restoring column state that I had been hitting.  This also feels like a regression, as I seemed to remember this being an issue that was reported and fixed quite some time ago.

Thanks.

-Eric