dovecot - Apr 2015 - dovecot crash with virtual folders (debian testing version 2.2.13-11)

The virtual folder triggering the crash has the configuration

namespace {
  prefix = virtual/
  separator = /
  location = virtual:~/Maildir/virtual
}

And the actual virtual/openstack/dovecot-virtual file is

Lists/openstack-dev
  inthread refs or from "james bottomley" keyword thread

It's a standard search for threads I've either replied to or marked with
an imap keyword 'thread'

The imap command

0 status virtual/openstack (MESSAGES UNSEEN RECENT)

Is crashing most of the time with

gdb /usr/lib/dovecot/imap
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Reading symbols from /usr/lib/dovecot/imap...Reading symbols
from /usr/lib/debug//usr/lib/dovecot/imap...done.
done.
(gdb) r
Starting program: /usr/lib/dovecot/imap 
process 7868 is executing new program: /usr/bin/doveconf
process 7868 is executing new program: /usr/lib/dovecot/imap
* PREAUTH [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID
ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS
THREAD=ORDEREDSUBJECT MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN
NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH
ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE BINARY
MOVE] Logged in as jejb
0 status virtual/openstack (MESSAGES UNSEEN RECENT)

Program received signal SIGSEGV, Segmentation fault.
0xb7f0814b in mail_search_args_deinit_sub (args=args at entry=0x8005caf0, 
    arg=0x8005cb08) at mail-search.c:169
169     mail-search.c: No such file or directory.
(gdb) bt
#0  0xb7f0814b in mail_search_args_deinit_sub
(args=args at entry=0x8005caf0, 
    arg=0x8005cb08) at mail-search.c:169
#1  0xb7f08aea in mail_search_args_deinit (args=0x8005caf0)
    at mail-search.c:193
#2  0xb7d9ecf1 in virtual_mailbox_close_internal
(mbox=mbox at entry=0x800585d0)
    at virtual-storage.c:253
#3  0xb7d9ed7b in virtual_mailbox_close (box=0x800585d0)
    at virtual-storage.c:307
#4  0xb7f403ff in mail_thread_mailbox_close (box=0x800585d0)
    at index-thread.c:628
#5  0xb7f0d3fe in mailbox_close (box=0x800585d0) at mail-storage.c:1182
#6  0xb7f0d472 in mailbox_free (_box=0xbffff878) at mail-storage.c:1197
#7  0x8001e0ae in imap_status_get (cmd=0x80053948, ns=0x80052220, 
    mailbox=0x8003a250 "virtual/openstack", items=0xbffff8f8, 
    result_r=0xbffff900) at imap-status.c:96
#8  0x80011f64 in cmd_status (cmd=0x80053948) at cmd-status.c:40
#9  0x80016847 in command_exec (cmd=0x80053948) at imap-commands.c:158
#10 0x800155cb in client_command_input (cmd=0x80053948) at
imap-client.c:778
#11 0x80015719 in client_command_input (cmd=0x80053948) at
imap-client.c:839
#12 0x800159cd in client_handle_next_command (remove_io_r=<synthetic
pointer>, 
    client=0x80052ee0) at imap-client.c:877
#13 client_handle_input (client=0x80052ee0) at imap-client.c:889
#14 0x80015dd5 in client_input (client=0x80052ee0) at imap-client.c:931
---Type <return> to continue, or q <return> to quit---
#15 0xb7e202e3 in io_loop_call_io (io=0x800538c8) at ioloop.c:441
#16 0xb7e214be in io_loop_handler_run_internal (ioloop=0x80042458)
    at ioloop-epoll.c:220
#17 0xb7e2036a in io_loop_handler_run (ioloop=0x80042458) at
ioloop.c:488
#18 0xb7e203f9 in io_loop_run (ioloop=0x80042458) at ioloop.c:465
#19 0xb7dc6985 in master_service_run (service=0x80042380, 
    callback=0x800200b0 <client_connected>) at master-service.c:566
#20 0x80008b44 in main (argc=1, argv=0xbffffd84) at main.c:400

I thought it might be this patch

http://hg.dovecot.org/dovecot-2.2/rev/5c6f49e2d8d9

But after applying I still get the same segfault.

James