Hi,

I am trying to test an actor I wrote with 8sync. I created a probe actor
which sends messages to the main one. A problem I am having is that when
I want to send a *cleanup* to the main (server) actor from the probe, I
am getting the following backtrace:

--8<---------------cut here---------------start------------->8---
λ guile --debug -s tests/test.scm
Backtrace:
In ice-9/boot-9.scm:
  1736:10 11 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          10 (apply-smob/0 #<thunk 7fac09a7b9a0>)
In ice-9/boot-9.scm:
    718:2  9 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8  8 (_ #(#(#<directory (guile-user) 7fac096a0f00>)))
In ice-9/boot-9.scm:
   2806:4  7 (save-module-excursion _)
  4351:12  6 (_)
In 8sync/actors.scm:
    812:6  5 (run-hive #<<hive> 7fac08bdd0c0> _ #:cleanup _ # _)
In ice-9/control.scm:
    91:24  4 (call-with-escape-continuation _)
In 8sync/agenda.scm:
    569:6  3 (run-agenda #<<agenda> queue: (() . #f) prompt-tag: ("…> …)
    470:7  2 (update-agenda-from-select! #<<agenda> queue: (() . #f)…>)
In ice-9/boot-9.scm:
  1731:15  1 (with-exception-handler #<procedure 7fac08bbd240 at ic…> …)
In unknown file:
           0 (select (#<closed: file 7fac07ff6460>) () () #f #f)

ERROR: In procedure select:
In procedure select: Wrong type argument in position 1: #<closed: file 7fac07ff6460>
--8<---------------cut here---------------end--------------->8---

I have attached a simple snippet to reproduce the problem, and also a
naive patch I did. I am not sure if it is me doing the shutdown wrong, or
it's a bug.

-- 
Alexey