TypeError due to "size" being None in pyfilesystem+dokan

[zooko]

I saw this bug report to pyfilesystem:

​http://code.google.com/p/pyfilesystem/issues/detail?id=96

tahoe-lafs 1.9.0 + pyfilesystem 0.4 (and svn r723) + dokan 0.6.0
OS Windows 7 x64 Russian + Python 2.7.2 x86

Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 313, in 'calling callback function'
  File "C:\Program Files (x86)\Python27\lib\site-packages\fs\expose\dokan\__init__.py", line 256, in wrapper
    return func(self,*args)
  File "C:\Program Files (x86)\Python27\lib\site-packages\fs\expose\dokan\__init__.py", line 173, in wrapper
    res = func(*args,**kwds)
  File "C:\Program Files (x86)\Python27\lib\site-packages\fs\errors.py", line 191, in wrapper
    return func(*args,**kwds)
  File "C:\Program Files (x86)\Python27\lib\site-packages\fs\expose\dokan\__init__.py", line 604, in FindFilesWithPattern
    data = self._info2finddataw(fpath,finfo,None)
  File "C:\Program Files (x86)\Python27\lib\site-packages\fs\expose\dokan\__init__.py", line 794, in _info2finddataw
    data.nFileSizeHigh = info.get("size",0) >> 32
TypeError: unsupported operand type(s) for >>: 'NoneType' and 'int'

As far as I know, pyfilesystem doesn't have a strong test suite, so it will require more effort from someone to figure out where exactly the problem lies in pyfilesystem, Tahoe-LAFS, dokan, or the interfaces between them...