bup web error

mc@Debian-101-buster-64-minimal:~/backups$ bup web :8090
Serving HTTP on 0.0.0.0:8090...
Handling request for b'/'
fatal: git show-ref: bad ref refs/heads/survival (8c03f9045d38524f25596ec5b75c54d1ff5ef22e)
Uncaught exception GET / (totallylegit.ip.goes.here)
HTTPServerRequest(protocol='http', host='bismuth.be:8090', method='GET', uri='/', version='HTTP/1.1', remote_ip='totallylegit.ip.goes.here')
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/tornado/web.py", line 1788, in _execute
    result = method(*self.path_args, **self.path_kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/bup/bup/cmd/web.py", line 122, in get
    return self._process_request(path)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/bup/bup/cmd/web.py", line 139, in _process_request
    self._list_directory(path, res)
  File "/usr/lib/bup/bup/cmd/web.py", line 159, in _list_directory
    self.render(
  File "/usr/lib/python3/dist-packages/tornado/web.py", line 944, in render
    html = self.render_string(template_name, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/tornado/web.py", line 1093, in render_string
    return t.generate(**namespace)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/tornado/template.py", line 362, in generate
    return execute()
           ^^^^^^^^^
  File "list-directory_html.generated.py", line 38, in _tt_execute
    for (display, link, size) in dir_contents:  # list-directory.html:30
  File "/usr/lib/bup/bup/cmd/web.py", line 99, in _dir_contents
    for name, item in vfs.contents(repo, dir_item):
  File "/usr/lib/bup/bup/vfs.py", line 927, in contents
    for x in item_gen:
  File "/usr/lib/bup/bup/vfs.py", line 604, in root_items
    for name, oid in tuple(repo.refs([], limit_to_heads=True)):
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/bup/bup/repo.py", line 78, in refs
    for ref in git.list_refs(patterns=patterns,
  File "/usr/lib/bup/bup/git.py", line 1048, in list_refs
    assert(not out)
           ^^^^^^^
AssertionError
500 GET / (totallylegit.ip.goes.here) 75.40ms