[Dovecot] panic in dovecot when using fts with solr

[André Rodier]

This is my doveconf output. Please, note that since the panic, I have
switched to fts with squat, but it is very limited for large
mailboxes.

Any idea how to fix this?

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-amd64 x86_64 Debian 7.0
auth_default_realm = indiefield.co.uk
auth_master_user_separator = :
auth_mechanisms = plain login
auth_username_chars =
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890 .-_@
auth_username_translation = "- _ "
auth_verbose = yes
disable_plaintext_auth = no
dotlock_use_excl = no
hostname = smtp.indiefield.org.uk
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
lock_method = dotlock
mail_access_groups = vmail
mail_fsync = always
mail_gid = vmail
mail_location = maildir:~/Mails/Maildir/:INDEX=~/Mails/Indexes/
mail_plugins = autocreate quota acl virtual listescape fts fts_squat
mail_privileged_group = vmail
mail_uid = vmail
maildir_copy_with_hardlinks = no
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope
encoded-character vacation subaddress comparator-i;ascii-numeric
relational regex imap4flags copy include variables body enotify
environment mailbox date ihave
mmap_disable = yes
namespace {
  hidden = no
  inbox = no
  list = yes
  location = maildir:/var/vmail/%d/Public/Mails/Maildir/:INDEX=~/Mails/PublicIndexes/
  prefix = Public/
  separator = /
  subscriptions = yes
  type = public
}
namespace {
  list = children
  location = maildir:%%h/Mails/Maildir/:INDEX=~/Mails/SharedIndexes/%%u
  prefix = Shared/%%d/%%n/
  separator = /
  subscriptions = no
  type = shared
}
namespace inbox {
  hidden = no
  inbox = yes
  list = yes
  location = maildir:~/Mails/Maildir/:INDEX=~/Mails/Indexes/
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix =
  separator = /
  subscriptions = yes
  type = private
}
passdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
plugin {
  acl = vfile:/etc/dovecot/global-acls:cache_secs=300
  acl_anyone = allow
  acl_shared_dict = file:/var/vmail/indiefield.co.uk/shared-mailboxes
  autocreate = Trash
  autocreate2 = Drafts
  autocreate3 = Sent
  autocreate4 = Junk
  autocreate5 = Archives
  autosubscribe = Trash
  autosubscribe2 = Drafts
  autosubscribe3 = Sent
  autosubscribe4 = Junk
  autosubscribe5 = Archives
  fts = squat
  fts_squat = partial=4 full=10
  listescape_char = %%
  quota = maildir:User quota
  quota_warning = storage=95%% quota-warning 95 %u
  sieve = ~/Mails/.dovecot.sieve
  sieve_after = %h/Mails/Sieve/After/
  sieve_before = /etc/dovecot/sieve-default/before/
  sieve_dir = ~/Mails/Sieve
  sieve_max_script_size = 4M
}
protocols = " imap lmtp sieve pop3"
service auth-worker {
  user = vmail
}
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = vmail
    mode = 0666
    user = postfix
  }
  unix_listener auth-userdb {
    group = vmail
    mode = 0666
    user = postfix
  }
  user = vmail
}
service dict {
  unix_listener dict {
    group = vmail
    mode = 0600
    user = vmail
  }
}
service director {
  fifo_listener login/proxy-notify {
    group = postfix
    mode = 0666
    user = postfix
  }
  unix_listener director-userdb {
    group = postfix
    mode = 0600
    user = postfix
  }
  unix_listener login/director {
    group = postfix
    mode = 0666
    user = postfix
  }
}
service lmtp {
  group = vmail
  inet_listener lmtp {
    port = 24
  }
  user = vmail
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
}
service quota-warning {
  executable = script /etc/dovecot/scripts/quota-warning.sh
  unix_listener quota-warning {
    user = vmail
  }
  user = dovecot
}
ssl_cert = </etc/apache2/certs/generic.indiefield.org.uk.crt
ssl_key = </etc/apache2/certs/generic.indiefield.org.uk.key
userdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol lmtp {
  mail_plugins = quota sieve virtual
}
protocol lda {
  auth_socket_path = /var/run/dovecot/auth-userdb
}
protocol imap {
  mail_plugins = autocreate quota acl virtual listescape fts fts_squat
imap_quota imap_acl autocreate
}