unity-greeter crashed with SIGSEGV in g_type_check_instance_is_a()

[Stuart Langridge]

System hung while doing a dist-upgrade. After reboot, system came back up in "low graphics" mode. After completing the upgrade and rebooting again, many error dialogs were shown; this was one.

ProblemType: Crash
DistroRelease: Ubuntu 13.10
Package: unity-greeter 13.10.2-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-5.11-generic 3.11.0
Uname: Linux 3.11.0-5-generic x86_64
ApportVersion: 2.12.1-0ubuntu3
Architecture: amd64
Date: Mon Sep 9 22:46:49 2013
ExecutablePath: /usr/sbin/unity-greeter
ExecutableTimestamp: 1376441876
InstallationDate: Installed on 2011-12-11 (638 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20111211)
MarkForUpload: True
ProcCmdline: /usr/sbin/unity-greeter
ProcCwd: /var/lib/lightdm
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/false
SegvAnalysis:
 Segfault happened at: 0x7fb1370f5c9c <g_type_check_instance_is_a+60>: testb $0x4,0x16(%r8)
 PC (0x7fb1370f5c9c) ok
 source "$0x4" ok
 destination "0x16(%r8)" (0x686374614d646456) not located in a known VMA region (needed writable region)!
SegvReason: writing unknown VMA
Signal: 11
SourcePackage: unity-greeter
StacktraceTop:
 g_type_check_instance_is_a () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 lightdm_layout_get_name () from /usr/lib/liblightdm-gobject-1.so.0
 lightdm_get_layout () from /usr/lib/liblightdm-gobject-1.so.0
 ?? ()
 ?? ()
Title: unity-greeter crashed with SIGSEGV in g_type_check_instance_is_a()
UpgradeStatus: Upgraded to saucy on 2013-09-05 (4 days ago)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 g_type_check_instance_is_a (type_instance=type_instance@entry=0x131e720, iface_type=<optimized out>) at /build/buildd/glib2.0-2.37.6/./gobject/gtype.c:3975
 lightdm_layout_get_name (layout=0x131e720) at layout.c:211
 lightdm_get_layout () at layout.c:187
 menu_bar_set_layouts (self=0x10e61c0, layouts=0x0) at menubar.c:513
 _user_list___lambda28_ (self=0x11e4570) at user-list.c:7017