Comment 2 for bug 1037811

StacktraceTop:
 g_mutex_get_impl (mutex=0xaaaaaaaaaaaaaab2) at /build/buildd/glib2.0-2.33.8/./glib/gthread-posix.c:119
 g_mutex_lock (mutex=mutex@entry=0xaaaaaaaaaaaaaab2) at /build/buildd/glib2.0-2.33.8/./glib/gthread-posix.c:208
 external_thumbnailers_disabled_changed_cb (settings=<optimized out>, key=<optimized out>, factory=<optimized out>) at gnome-desktop-thumbnail.c:722
 g_cclosure_marshal_VOID__STRINGv (closure=0x28ae600, return_value=<optimized out>, instance=0x287bca0, args=<optimized out>, marshal_data=<optimized out>, n_params=<optimized out>, param_types=0x1860b80) at /build/buildd/glib2.0-2.33.8/./gobject/gmarshal.c:1004
 _g_closure_invoke_va (closure=0x28ae600, return_value=0x0, instance=0x287bca0, args=0x7fff128b03a8, n_params=1, param_types=0x1860b80) at /build/buildd/glib2.0-2.33.8/./gobject/gclosure.c:840