BlockDownloadStream class in sdo\client.py appears to be missing an object definition

[Eqqm4n]

Hello-
In sdo\client.py the BlockDownloadStream class refers to the self.crc_supported attribute on lines 680, 738, and 812, but this class attribute does not appear to be defined (and as a side note, the BlockUploadStream class does define one).

I ran across this issue when a host's block transfer request was rejected by the device, causing the library to go down one of these broken code paths:

2026-01-05 14:42:37,387 - canopen_client - ERROR - Full traceback:
Traceback (most recent call last):
  File "C:\nVent_work\zephyr_root\zephyr_repo\nvent_projects\canopen_sim\canopen_sim\canopen_client.py", line 724, in upload_firmware
    with self.node.sdo.open(index, subindex, "wb",
         ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
                          size=total_size,
                          ^^^^^^^^^^^^^^^^
                          block_transfer=True) as fp:
                          ^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python313\Lib\site-packages\canopen\sdo\client.py", line 213, in open
    raw_stream = BlockDownloadStream(self, index, subindex, size, request_crc_support=request_crc_support)
  File "C:\Program Files\Python313\Lib\site-packages\canopen\sdo\client.py", line 655, in __init__
    response = sdo_client.request_response(request)
  File "C:\Program Files\Python313\Lib\site-packages\canopen\sdo\client.py", line 86, in request_response
    return self.read_response()
           ~~~~~~~~~~~~~~~~~~^^
  File "C:\Program Files\Python313\Lib\site-packages\canopen\sdo\client.py", line 74, in read_response
    raise SdoAbortedError(abort_code)
canopen.sdo.exceptions.SdoAbortedError: Code 0x05040001, Unknown SDO command specified
2026-01-05 14:42:37,391 - canopen_client - ERROR - Error uploading firmware: Code 0x05040001, Unknown SDO command specified
Exception ignored in: <canopen.sdo.client.BlockDownloadStream object at 0x000001F2DDEF6A40>
Traceback (most recent call last):
  File "C:\Program Files\Python313\Lib\site-packages\canopen\sdo\client.py", line 793, in close
    if self.crc_supported:
AttributeError: 'BlockDownloadStream' object has no attribute 'crc_supported'
2026-01-05 14:42:38,548 - canopen_client - INFO - Disconnected from CAN bus