Stem tracebacks when parsing bridge extra-info descriptor

Looks like Stem doesn't like the "bridge-ip-versions " line in the attached bridge extra-info descriptors. Here's the traceback using a slightly modified log message to include more details:

Traceback (most recent call last):
  File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.6/threading.py", line 484, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/reader.py", line 425, in _read_descriptor_files
    self._handle_walker(walker, new_processed_files)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/reader.py", line 453, in _handle_walker
    self._handle_file(os.path.join(root, filename), new_processed_files)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/reader.py", line 498, in _handle_file
    self._handle_descriptor_file(target, target_type)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/reader.py", line 509, in _handle_descriptor_file
    for desc in stem.descriptor.parse_file(target, target_file):
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/__init__.py", line 105, in parse_file
    for desc in file_parser(descriptor_file):
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/__init__.py", line 133, in _parse_metrics_file
    yield stem.descriptor.extrainfo_descriptor.BridgeExtraInfoDescriptor(descriptor_file.read())
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/extrainfo_descriptor.py", line 858, in __init__
    super(BridgeExtraInfoDescriptor, self).__init__(raw_contents, validate)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/extrainfo_descriptor.py", line 413, in __init__
    self._parse(entries, validate)
  File "/home/karsten/tasks/task-7828/stem/stem/descriptor/extrainfo_descriptor.py", line 882, in _parse
    raise stem.ProtocolError("The bridge-ip-versions should be a comma separated listing of '<protocol>=<count>' mappings: '%s' (entry = '%s')" % (line, entry, ))
ProtocolError: The bridge-ip-versions should be a comma separated listing of '<protocol>=<count>' mappings: 'bridge-ip-versions ' (entry = '')