handle dulwich.objects.EmptyFileException

[jelmer]

This one is pretty obscure, but Dulwich may raise EmptyFileException when part of the repository is corrupted. It would be nice if klaus displayed an appropriate error page.

  File "/usr/local/lib/python3.10/dist-packages/klaus/views.py", line 332, in make_template_context
    super(IndexView, self).make_template_context(*args)
  File "/usr/local/lib/python3.10/dist-packages/klaus/views.py", line 222, in make_template_context
    super(TreeViewMixin, self).make_template_context(*args)
  File "/usr/local/lib/python3.10/dist-packages/klaus/views.py", line 184, in make_template_context
    repo, rev, path, commit = _get_repo_and_rev(repo, namespace, rev, path)
  File "/usr/local/lib/python3.10/dist-packages/klaus/views.py", line 111, in _get_repo_and_rev
    rev = repo.get_default_branch()
  File "/usr/local/lib/python3.10/dist-packages/klaus/repo.py", line 147, in get_default_branch
    for name in self.get_branch_names():
  File "/usr/local/lib/python3.10/dist-packages/klaus/repo.py", line 182, in get_branch_names
    return self.get_ref_names_ordered_by_last_commit("refs/heads", exclude)
  File "/usr/local/lib/python3.10/dist-packages/klaus/repo.py", line 175, in get_ref_names_ordered_by_last_commit
    sorted_names = sorted(refs.keys(), key=get_commit_time, reverse=True)
  File "/usr/local/lib/python3.10/dist-packages/klaus/repo.py", line 163, in get_commit_time
    obj = self[refs[refname]]
  File "/code/dulwich/dulwich/repo.py", line 783, in __getitem__
    return self.object_store[name]
  File "/code/dulwich/dulwich/object_store.py", line 144, in __getitem__
    type_num, uncomp = self.get_raw(sha)
  File "/code/dulwich/dulwich/object_store.py", line 581, in get_raw
    ret = self._get_loose_object(hexsha)
  File "/code/dulwich/dulwich/object_store.py", line 745, in _get_loose_object
    return ShaFile.from_path(path)
  File "/code/dulwich/dulwich/objects.py", line 422, in from_path
    return cls.from_file(f)
  File "/code/dulwich/dulwich/objects.py", line 428, in from_file
    obj = cls._parse_file(f)
  File "/code/dulwich/dulwich/objects.py", line 396, in _parse_file
    raise EmptyFileException("Corrupted empty file detected")
dulwich.objects.EmptyFileException: Corrupted empty file detected </div>