get errors out on malformed HTTP response

The get command will cause the following Traceback on a malformed HTTP response:

ERROR core.dispatcher: Exception occured in HTTP processor of network plugin.
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/Ibid-0.1.0-py2.6.egg/ibid/core.py", line 32, in _process
    processor.process(event)
  File "/usr/local/lib/python2.6/dist-packages/Ibid-0.1.0-py2.6.egg/ibid/plugins/__init__.py", line 144, in process
    method(event, *match.groups())
  File "/usr/local/lib/python2.6/dist-packages/Ibid-0.1.0-py2.6.egg/ibid/plugins/network.py", line 275, in get
    if (content_type.startswith('text/html') or
AttributeError: 'NoneType' object has no attribute 'startswith'

To reproduce:

Run netcat on a public server:
    $ nc -l 5000

Instruct the bot to fetch the page:
    bot: get xxx.xxx.xxx:5000

You'll see the following come through in the nc session:

    GET http://xxx.xxx.xxx:5000/ HTTP/1.1
    Host: xxx.xxx.xx:5000
    Accept-Encoding: identity
    Range: bytes=0-2048

Respond with the following (without indents):

    HTTP/1.1 502 Foo Bar

    ^C

It's potentially a vulnerability, but I haven't checked further. It also looks like it's an error in an included lib rather than ibid itself.