[imp] Document contained no data - need no registry

[Chuck Hagenbuch]

Quoting Yevgeniy Miretskiy <eugene@invision.net>:

> I'll give this a shot.  However, the 9908 bug is executed when
>     running against a mailbox without any UNSEEN messages, apache dies.

It was actually any time imap_sort returned no messages (though only on certain 
IMAP servers - seemingly anything other than UW, actually). Anyway, if you look 
at the backtraces, they were crashing on the same piece of code, so it's a 
pretty good bet that the same fix will apply.

-chuck

--
Charles Hagenbuch, <chuck@horde.org>

Taurus:
You will receive an urgent transmission from the Martian government informing 
you that Mars does not, in fact, need women, so please stop sending them.