dovecot - Jul 2013 - Dovecot 2.2.4 : Panic: file pop3-client.c: line 585 (client_default_destroy): assertion failed: (client->cmd == NULL)

This doesn't seem to affect clients, but I'm seeing an occasional pop3
error in the log over the last week.
Any ideas what is causing this?
Thanks,
Ken
> Jul  4 15:04:03 mail dovecot: POP3(user)x.x.x.x: Connection
> closed top=0/0, retr=0/0, del=0/4582, size=246709805
> Jul  4 15:04:03 mail dovecot: POP3(user)x.x.x.x: Panic: file
> pop3-client.c: line 585 (client_default_destroy): assertion failed:
> (client->cmd == NULL)
> Jul  4 15:04:03 mail dovecot: POP3(user)x.x.x.x: Error: Raw
> backtrace: /usr/lib/dovecot/libdovecot.so.0() [0x31b4c6074a] ->
> /usr/lib/dovecot/libdovecot.so.0() [0x31b4c60796] ->
> /usr/lib/dovecot/libdovecot.so.0(i_error+0) [0x31b4c202df] ->
> dovecot/pop3() [0x404df9] -> dovecot/pop3(client_handle_input+0xd4)
> [0x4051b4] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x36)
> [0x31b4c6f6d6] ->
> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0xa7)
> [0x31b4c70737] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x28)
> [0x31b4c6f678] ->
> /usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13)
> [0x31b4c24fa3] -> dovecot/pop3(main+0x257) [0x4043d7] ->
> /lib64/libc.so.6(__libc_start_main+0xfd) [0x3a08e1ecdd] ->
> dovecot/pop3() [0x403f29]
> Jul  4 15:04:04 mail dovecot: POP3(user)x.x.x.x: Fatal: master:
> service(pop3): child 9080 killed with signal 6 (core dumped)

-- 
Ken Anderson
Pacific Internet - http://www.pacific.net

On 5.7.2013, at 21.02, Ken A <ka at pacific.net> wrote:
> This doesn't seem to affect clients, but I'm seeing an occasional
pop3
> error in the log over the last week.
> Any ideas what is causing this?
..
>> Jul  4 15:04:03 mail dovecot: POP3(user)x.x.x.x: Connection
>> closed top=0/0, retr=0/0, del=0/4582, size=246709805
> 
>> Jul  4 15:04:03 mail dovecot: POP3(user)x.x.x.x: Panic: file
>> pop3-client.c: line 585 (client_default_destroy): assertion failed:
>> (client->cmd == NULL)
The only reason I can see for this is:
http://hg.dovecot.org/dovecot-2.2/rev/debbcfe5577a