"Wrong type argument: arrayp, nil" due to elmo-network-session-idle-timeout

Hi,

Recently I had to recreate the elmo msgdb on a big multi-folder
(30,000+ messages) and I got the error "(wrong-type-argument arrayp
nil)".

In my case that was *not* caused by a too-small
`elmo-multi-divide-number' but because my config had
`elmo-network-session-idle-timeout' set to a small value. Resetting it
to the default value (nil) solved my issue.

It seems that when `elmo-network-session-idle-timeout' is set to a
small value, and it takes a very long time to construct the msgdb and
summary, the required data disappears before the operation is
completely finished.

Perhaps this is of use to others.

Regards
Pascal