Illegal value for type parameter leads to uncaught exception in Pyonionoo

Asking for type=bridges lead to the following exception on the server and a 500 Internal Server Error response instead of the expected 400 Bad Request.

2012-09-23 20:47:18+0200 [-] [Failure instance: Traceback: <type
  'exceptions.ValueError'>: zero length field name in format
	/usr/lib/python2.6/dist-packages/twisted/internet/defer.py:
  345:errback
	/usr/lib/python2.6/dist-packages/twisted/internet/defer.py:
  424:_startRunCallbacks
	/usr/lib/python2.6/dist-packages/twisted/internet/defer.py:
  441:_runCallbacks
	/usr/lib/python2.6/dist-packages/twisted/internet/defer.py:
  949:gotResult
	--- <exception caught here> ---
	/usr/lib/python2.6/dist-packages/twisted/internet/defer.py:
  891:_inlineCallbacks
	/usr/lib/python2.6/dist-packages/twisted/python/failure.py:
  338:throwExceptionIntoGenerator
	/home/karsten/src/pyonionoo/pyonionoo/handlers/summary.py:
  27:get
	/usr/lib/python2.6/dist-packages/twisted/python/threadpool.py:
  207:_worker
	/usr/lib/python2.6/dist-packages/twisted/python/context.py:
  59:callWithContext
	/usr/lib/python2.6/dist-packages/twisted/python/context.py:
  37:callWithContext
	/home/karsten/src/pyonionoo/pyonionoo/handlers/summary.py:
  32:_get_results
	/home/karsten/src/pyonionoo/pyonionoo/handlers/arguments.py:
  64:parse
	]
2012-09-23 20:47:18+0200 [-] Uncaught exception GET
  /summary?type=bridges (127.0.0.1) :: HTTPRequest(protocol='http',
  host='localhost:8888', method='GET', uri='/summary?type=bridges',
  version='HTTP/1.1', remote_ip='127.0.0.1', body='', headers={'Host':
  'localhost:8888', 'Accept': '*/*', 'User-Agent': 'curl/7.21.0
  (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/1.2.3.4
  libidn/1.15 libssh2/1.2.6'})
2012-09-23 20:47:18+0200 [-] 500 GET /summary?type=bridges (127.0.0.1)
  2.29ms

(Added a few line breaks to the output above.)

Asking for an invalid "running" parameter value leads to a similar result. There may be more cases where parameters are not checked as thoroughly as they should.