Return key press on qlog causes error dialog

[Craig Hewetson]

Reproduce:
1) open qlog.
2) Without doing anything else, press "enter" key.

Result:
bzr: ERROR: exceptions.IndexError: list index out of range

Traceback (most recent call last):
  File "/home/craig/.bazaar/plugins/qbzr/lib/logwidget.py", line 256, in keyPressEvent
    self.default_action()
  File "/home/craig/.bazaar/plugins/qbzr/lib/logwidget.py", line 319, in default_action
    self.show_diff(index)
  File "/home/craig/.bazaar/plugins/qbzr/lib/logwidget.py", line 325, in show_diff
    new_revid, old_revid = self.get_selection_top_and_parent_revids(index)
  File "/home/craig/.bazaar/plugins/qbzr/lib/logwidget.py", line 301, in get_selection_top_and_parent_revids
    top_revid = str(indexes[0].data(logmodel.RevIdRole).toString())
IndexError: list index out of range

bzr 2.0.0 on python 2.6.2 (linux2)
arguments: ['/usr/bin/bzr', 'qlog']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_ZA.UTF-8'
plugins:
  bzrtools /usr/lib/python2.6/dist-packages/bzrlib/plugins/bzrtools [2.0.0]
  email /home/craig/.bazaar/plugins/email [unknown]
  explorer /home/craig/.bazaar/plugins/explorer [0.8.2]
  extmerge /home/craig/.bazaar/plugins/extmerge [unknown]
  fix_compare /home/craig/.bazaar/plugins/fix_compare [0.1.0dev]
  gtk /home/craig/.bazaar/plugins/gtk [0.98.0dev1]
  launchpad /usr/lib/python2.6/dist-packages/bzrlib/plugins/launchpad [2.0.0]
  netrc_credential_store /usr/lib/python2.6/dist-packages/bzrlib/plugins/netrc_credential_store [2.0.0]
  qbzr /home/craig/.bazaar/plugins/qbzr [0.15.0dev]
  search /home/craig/.bazaar/plugins/search [1.7.0dev]
  stats /home/craig/.bazaar/plugins/stats [unknown]
  text_checker /home/craig/.bazaar/plugins/text_checker [0.3.0dev1]
  xmloutput /home/craig/.bazaar/plugins/xmloutput [0.8.5]