IDLE bug fixed

[Philip Van Hoof <spam pvanhoof be>]

When the folder had no items, the reason-to-live value for the
priv->folder instance was also immediately none. Therefore priv->folder
got immediately destroyed. This destruction of the instance meant that
the IDLE checking (Push E-mail feature) was also stopped at the finalise
of the CamelImapFolder type.

I fixed this by aborting the uncache of an empty folder: empty folders
are the exception here (an empty folder is kept alive, so that its IDLE
functionality keeps working).

Empty folders don't consume a lot RAM, and once a first header arrives
in the folder, it will be dealt with just like any other folder (it'll
get uncached asa->p<-).


ps. The uncaching & caching of folders in Tinymail is tricky stuff, so
know what you are doing when changing this (and I will of course review
changes in this area with Argus eyes). A lot of this defines the memory
usage of the framework, indeed.

-- 
Philip Van Hoof, software developer
home: me at pvanhoof dot be 
gnome: pvanhoof at gnome dot org 
http://www.pvanhoof.be/blog