gdebi crashes with : KeyError: "The cache has no package named 'opera-next'" when package is not in the archive

I downloaded a .deb package from internet. After trying to open it with GDebi to install it, GDebi window opens and loads it. When the progress bar completely fills, GDebi window closes unexpectly.

TEST CASE:
1. Download opera-next
 $ wget http://deb.opera.com/opera-beta/pool/non-free/o/opera-next/opera-next_11.50.1052_i386.deb
2. Run gdebi
 $ gdebi-gtk opera-next/opera-next_11.50.1052_i386.deb

Results:
 Traceback (most recent call last):
   File "/usr/bin/gdebi-gtk", line 73, in <module>
     app = GDebi(datadir=data,options=options,file=afile)
   File "/usr/share/gdebi/GDebi/GDebi.py", line 148, in __init__
     self.open(file)
   File "/usr/share/gdebi/GDebi/GDebi.py", line 327, in open
     provides = self.compareProvides()
   File "/usr/share/gdebi/GDebi/GDebiCommon.py", line 129, in compareProvides
     pkg = self._cache[self._deb.pkgname].installed
   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 177, in __getitem__
     raise KeyError('The cache has no package named %r' % key)
 KeyError: "The cache has no package named 'opera-next'"

It is also reproducible with other known good .deb files that are not part of the archive, for example crossover pro.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: gdebi 0.8~exp2
ProcVersionSignature: Ubuntu 3.0-1.2-generic 3.0.0-rc3
Uname: Linux 3.0-1-generic i686
NonfreeKernelModules: wl
Architecture: i386
Date: Wed Jun 22 14:24:13 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=es_MX:en
 PATH=(custom, no user)
 LANG=es_MX
 LC_MESSAGES=es_MX.UTF-8
 SHELL=/bin/bash
SourcePackage: gdebi
UpgradeStatus: Upgraded to oneiric on 2011-06-17 (5 days ago)