module raises an exception when using detect_available_configs

[MattWoodhead]

Describe the bug
The can_sontheim module prevents the can.detect_available_configs function from the python-can library from working as it raises an exception

To Reproduce

• install python-can-sontheim module
• Run can.detect_available_configs()

Expected behavior
The sontehim bus should either be reported as available opr unavailable

Screenshots, Traceback, MRE

Cannot load SIE MT_API for Sontheim: The Sontheim API is currently only compatible with the 32 bit python interpreter
Traceback (most recent call last):

  File "C:\Python\lib\site-packages\spyder_kernels\py3compat.py", line 356, in compat_exec
    exec(code, globals, locals)

  File "c:\users\matth\documents\github\python-can-bluetooth\examples\bluetooth_tx_example.py", line 18, in <module>
    print(can.detect_available_configs())

  File "C:\Users\matth\AppData\Roaming\Python\Python39\site-packages\can\interface.py", line 176, in detect_available_configs
    bus_class._detect_available_configs()  # pylint: disable=protected-access

  File "c:\users\matth\documents\github\python-can-sontheim\can_sontheim\_canlib.py", line 406, in _detect_available_configs
    error_code = _CANLIB.canGetDeviceList(byref(devices_struct))

AttributeError: 'NoneType' object has no attribute 'canGetDeviceList'

Desktop (please complete the following information):

• OS: Windows 10 64 bit
• SIE Adapter: CANfox

Additional context
N/A