pcmanfm crashed with SIGSEGV in IA__gtk_widget_get_toplevel()

[Wiklund Olle]

I have a system based on vanilla Ubuntu with added [KLX]ubuntu-desktops. The crash comes when unmounting a partition on a hard drive. Pcmanfm's window disappears.

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: overlay-scrollbar 0.2.16-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-17.27-generic 3.2.6
Uname: Linux 3.2.0-17-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.95-0ubuntu1
Architecture: amd64
Date: Wed Mar 28 03:10:04 2012
ExecutablePath: /usr/bin/pcmanfm
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120228.1)
PackageArchitecture: all
ProcCmdline: pcmanfm --desktop --profile lubuntu
ProcEnviron:
 PATH=(custom, user)
 LANG=sv_SE.UTF-8
 SHELL=/bin/bash
SegvReason: reading unknown VMA
Signal: 11
SourcePackage: overlay-scrollbar
Title: pcmanfm crashed with SIGSEGV in gtk_widget_get_toplevel()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo

[Apport retracing service (apport)]

StacktraceTop:
 IA__gtk_widget_get_toplevel (widget=0xaaaaaaaaaaaaaaaa) at /build/buildd/gtk+2.0-2.24.10/gtk/gtkwidget.c:8218
 thumb_map_cb (widget=0x18f25c0, user_data=<optimized out>) at /build/buildd/overlay-scrollbar-0.2.16/./os/os-scrollbar.c:1926
 closure_invoke_notifiers (notify_type=2, closure=0x19a8a10) at /build/buildd/glib2.0-2.32.0/./gobject/gclosure.c:273
 _g_closure_invoke_va (closure=0x19a8a10, return_value=0x0, instance=0x1, args=0x7fff9b1f2670, n_params=0, param_types=<optimized out>) at /build/buildd/glib2.0-2.32.0/./gobject/gclosure.c:839
 ?? ()