gnome-sudoku crashed with AttributeError in cover_track(): 'NoneType' object has no attribute 'remove'

[Jeroen T. Vermeulen]

Automatically reported crash.

ProblemType: Crash
DistroRelease: Ubuntu 13.10
Package: gnome-sudoku 1:3.8.1-1
ProcVersionSignature: Ubuntu 3.11.0-9.16-generic 3.11.2
Uname: Linux 3.11.0-9-generic i686
ApportVersion: 2.12.5-0ubuntu1
Architecture: i386
Date: Sun Oct 13 12:55:19 2013
EcryptfsInUse: Yes
ExecutablePath: /usr/games/gnome-sudoku
InstallationDate: Installed on 2012-11-27 (319 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release i386 (20121017.2)
InterpreterPath: /usr/bin/python2.7
MarkForUpload: True
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/games/gnome-sudoku
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
PythonArgs: ['/usr/games/gnome-sudoku']
SourcePackage: gnome-sudoku
Title: gnome-sudoku crashed with AttributeError in cover_track(): 'NoneType' object has no attribute 'remove'
UpgradeStatus: Upgraded to saucy on 2013-08-05 (68 days ago)
UserGroups: adm cdrom dip libvirtd lpadmin plugdev sambashare sudo