software-center crashed with AttributeError in pkg_downloaded(): 'NoneType' object has no attribute 'filename'

I was just trying to install "Utilities Lens - Calculator" and crashed.

Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/appdetailsview.py", line 2008, in update_totalsize
    self.app.archive_suite)
  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 585, in get_total_size_on_install
    if not pkg_downloaded(pkg) and not pkg.package.installed:
  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 58, in pkg_downloaded
    filename = os.path.basename(pkg_version.filename)
AttributeError: 'NoneType' object has no attribute 'filename'

As at 2012-04-27 this is the #4 top crash in Ubuntu.

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: software-center 5.1.9
ProcVersionSignature: Ubuntu 3.2.0-17.26-generic-pae 3.2.6
Uname: Linux 3.2.0-17-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 1.91-0ubuntu1
Architecture: i386
Date: Sun Feb 19 16:49:42 2012
ExecutablePath: /usr/share/software-center/software-center
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/bin/software-center
PythonArgs: ['/usr/bin/software-center']
SourcePackage: software-center
Title: software-center crashed with AttributeError in pkg_downloaded(): 'NoneType' object has no attribute 'filename'
UpgradeStatus: Upgraded to precise on 2012-02-19 (0 days ago)
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