[Dovecot] cmd_append_continue_parsing assertion failure

[Mike Abbott]

Dovecot-1.1.14 on Mac OS X.
Panic: IMAP(user): file cmd-append.c: line 266  
(cmd_append_continue_parsing): assertion failed: (ctx->count == uid2 -  
uid1 + 1)

Trivially reproducible:
$ telnet mailserver 143
a login user password
b append inbox

Backtrace:
0   libSystem.B.dylib             	0x00007fff8458aa92 __kill + 10
1   libSystem.B.dylib             	0x00007fff84606a1c abort + 83
2   imap                          	0x0000000100069f3e  
default_fatal_finish + 70
3   imap                          	0x0000000100069f8c  
i_syslog_fatal_handler + 0
4   imap                          	0x00000001000696eb i_info + 0
5   imap                          	0x0000000100001406  
cmd_append_continue_parsing + 434
6   imap                          	0x00000001000017a3 cmd_append + 407
7   imap                          	0x000000010000677e  
client_command_input + 33
8   imap                          	0x000000010000693f  
client_command_input + 482
9   imap                          	0x0000000100006a3e  
client_handle_input + 239
10  imap                          	0x0000000100006bc2 client_input + 148
11  imap                          	0x0000000100070f83  
io_loop_handler_run + 272
12  imap                          	0x0000000100070348 io_loop_run + 55
13  imap                          	0x000000010000db95 main + 1635
14  imap                          	0x0000000100001010 start + 52