[tmux-nicklist-portable.pl] - print() on closed filehandle $fifo at line 213

This issue is not easy to reproduce so I try to explain the running environment first and when this issue specifically occurs. The running environment is:

`Irssi v1.4.5`

* ZNC has IRC user credentials and has active to the IRC network
* irrsi runs in tmux and is connected the `lo` loopback interface to locally running ZNC daemon

The running state is the IRC user session has been active for a long time (days/weeks). IRC connection drops and ZNC finished authenticating successfully.

After attaching the running tmux session the status logs writes following:
```
print() on closed filehandle $fifo at /home/needle/.irssi/scripts/autorun/tmux-nicklist-portable.pl line 213.
print() on closed filehandle $fifo at /home/needle/.irssi/scripts/autorun/tmux-nicklist-portable.pl line 213.
print() on closed filehandle $fifo at /home/needle/.irssi/scripts/autorun/tmux-nicklist-portable.pl line 213.
print() on closed filehandle $fifo at /home/needle/.irssi/scripts/autorun/tmux-nicklist-portable.pl line 213.
```

This does not happen when starting a new tmux session.

I try if it is possible to reproduce this without using ZNC. irssi directly connected to IRC network and needs to re-authenticate due to connection loss to IRC.