TB when cloning an SVN trunk into repo in "subversion" format

[Torsten Bronger]

I got the following TB when I tried to copy an SVN trunk with "bzr branch" into the current repository which I had created using the "subversion" format.

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

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 802, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 758, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 492, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 905, in run
    possible_transports=[to_transport])
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/remote.py", line 75, in sprout
    result_repo.fetch(repo, revision_id=revision_id)
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 873, in fetch
    return inter.fetch(revision_id=revision_id, pb=pb, find_ghosts=find_ghosts)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/commit.py", line 778, in fetch
    self.copy_content(revision_id=revision_id, pb=pb)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/commit.py", line 740, in copy_content
    revision_id = self.source.revision_parents(revision_id)[0]
IndexError: list index out of range

bzr 1.0.0 on python 2.5.1.final.0 (linux2)
arguments: ['/usr/bin/bzr', 'branch', 'https://svn.origo.ethz.ch/bobcat/trunk', 'svn-mirror']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'de_DE.UTF-8'
plugins:
  bzrtools /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.0.0]
  launchpad /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  multiparent /usr/lib/python2.5/site-packages/bzrlib/plugins/multiparent.pyc [unknown]
  svn /usr/lib/python2.5/site-packages/bzrlib/plugins/svn [0.4.6]