WebSockeProtocol reasonRaw has no attribute 'encode' on closed socket

I noticed today that when my browser tab holding my ongoing ws was put to sleep (tab suspender extension for chrome) that the crossbar.io router raised an exception:

2015-09-09T17:01:03-0400 [Router       1306] Unhandled Error
Traceback (most recent call last):
  File "/usr/lib/python3.4/site-packages/twisted/python/log.py", line 101, in callWithLogger
    return callWithContext({"system": lp}, func, *args, **kw)
  File "/usr/lib/python3.4/site-packages/twisted/python/log.py", line 84, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "/usr/lib/python3.4/site-packages/twisted/python/context.py", line 118, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python3.4/site-packages/twisted/python/context.py", line 81, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "/usr/lib/python3.4/site-packages/twisted/internet/posixbase.py", line 597, in _doReadOrWrite
    why = selectable.doRead()
  File "/usr/lib/python3.4/site-packages/twisted/internet/tcp.py", line 209, in doRead
    return self._dataReceived(data)
  File "/usr/lib/python3.4/site-packages/twisted/internet/tcp.py", line 215, in _dataReceived
    rval = self.protocol.dataReceived(data)
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/twisted/websocket.py", line 135, in dataReceived
    self._dataReceived(data)
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1313, in _dataReceived
    self.consumeData()
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1328, in consumeData
    while self.processData() and self.state != WebSocketProtocol.STATE_CLOSED:
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1480, in processData
    return self.processDataHybi()
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1791, in processDataHybi
    fr = self.onFrameEnd()
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1889, in onFrameEnd
    self.processControlFrame()
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 1945, in processControlFrame
    if self.onCloseFrame(code, reasonRaw):
  File "/usr/lib/python3.4/site-packages/autobahn-0.10.7-py3.4.egg/autobahn/websocket/protocol.py", line 863, in onCloseFrame
    self.sendCloseFrame(code=code, reasonUtf8=reasonRaw.encode("UTF-8"), isReply=True)
builtins.AttributeError: 'NoneType' object has no attribute 'encode'

2015-09-09T17:01:03-0400 [Router       1306] Connection to/from tcp4:127.0.0.1:57025 lost (<class 'AttributeError'>): 'NoneType' object has no attribute 'encode')

This is autobahn 10.5. Please also note that I did add the option "echo_close_codereason":true to my crossbar.io config.

Start in autobahn/websocket/protocol.py at onCloseFrame and processControlFrame, following the traceback from autobahn/twisted/websocket.py. Reproduce the closed-socket path with echo_close_codereason enabled and inspect how an absent reason is handled. Done means the connection-close path no longer raises AttributeError when the reason is None.