Docval shape cannot be checked on types without len

[rly]

When shape is defined for a docval argument and type can be an object that does not have a __len__, e.g. ElectricalSeries.data

class ElectricalSeries(TimeSeries):
    @docval(...
            {'name': 'data', 'type': ('array_data', 'data', TimeSeries),
             'shape': ((None, ), (None, None), (None, None, None)),
             'doc': 'The data this TimeSeries dataset stores. Can also store binary data e.g. image frames'},
             ...)

then doing a direct link between data of one ElectricalSeries and another:

ts1 = ElectricalSeries('test_ts1', [0, 1, 2, 3, 4, 5], region, timestamps=[0.0, 0.1, 0.2, 0.3, 0.4, 0.5])
ts2 = ElectricalSeries('test_ts2', ts1, region, timestamps=[0.0, 0.1, 0.2, 0.3, 0.4, 0.5])

results in the error:

Traceback (most recent call last):
  File "C:\Users\Ryan\Documents\NWB\temp\pynwb\tests\unit\test_ecephys.py", line 42, in test_timestamps_link
    ts2 = ElectricalSeries('test_ts2', ts1, region, timestamps=[0.0, 0.1, 0.2, 0.3, 0.4, 0.5])
  File "c:\users\ryan\documents\nwb\hdmf\src\hdmf\utils.py", line 379, in func_call
    allow_extra=allow_extra)
  File "c:\users\ryan\documents\nwb\hdmf\src\hdmf\utils.py", line 176, in __parse_args
    if not __shape_okay_multi(argval, arg['shape']):
  File "c:\users\ryan\documents\nwb\hdmf\src\hdmf\utils.py", line 71, in __shape_okay_multi
    return any(__shape_okay(value, a) for a in argshape)
  File "c:\users\ryan\documents\nwb\hdmf\src\hdmf\utils.py", line 71, in <genexpr>
    return any(__shape_okay(value, a) for a in argshape)
  File "c:\users\ryan\documents\nwb\hdmf\src\hdmf\utils.py", line 78, in __shape_okay
    if not len(valshape) == len(argshape):
TypeError: object of type 'NoneType' has no len()