qbrowse: ObjectNotLocked error expanding a folder in 2a branch

If you have a --2a formated branch, and then you run

bzr qbrowse -r -1

and then expand a folder, you will get this error.

bzr: ERROR: bzrlib.errors.ObjectNotLocked: <bzrlib.groupcompress._GCGraphIndex object at 0xa20b96c> is not locked

Traceback (most recent call last):
  File "/home/garyvdm/.bazaar/plugins/qbzr/lib/treewidget.py", line 495, in fetchMore
    self.load_dir(parent.internalId())
  File "/home/garyvdm/.bazaar/plugins/qbzr/lib/treewidget.py", line 414, in load_dir
    key=ModelItemData.dirs_first_sort_key)
  File "/home/garyvdm/.bazaar/plugins/qbzr/lib/treewidget.py", line 358, in revision_tree_get_children
    for child in item_data.item.children.itervalues():
  File "/usr/lib/python2.6/dist-packages/bzrlib/inventory.py", line 2024, in children
    key_filter=[(self.file_id,)]):
  File "/usr/lib/python2.6/dist-packages/bzrlib/chk_map.py", line 983, in iteritems
    for node, node_filter in self._iter_nodes(store, key_filter=key_filter):
  File "/usr/lib/python2.6/dist-packages/bzrlib/chk_map.py", line 1125, in _iter_nodes
    for record in stream:
  File "/usr/lib/python2.6/dist-packages/bzrlib/groupcompress.py", line 1190, in get_record_stream
    orig_keys, ordering, include_delta_closure):
  File "/usr/lib/python2.6/dist-packages/bzrlib/groupcompress.py", line 1295, in _get_remaining_record_stream
    locations = self._index.get_build_details(keys)
  File "/usr/lib/python2.6/dist-packages/bzrlib/groupcompress.py", line 1764, in get_build_details
    self._check_read()
  File "/usr/lib/python2.6/dist-packages/bzrlib/groupcompress.py", line 1688, in _check_read
    raise errors.ObjectNotLocked(self)
ObjectNotLocked: <bzrlib.groupcompress._GCGraphIndex object at 0xa20b96c> is not locked