Fix "Bad file descriptor" error when closing the serial transport

[kristkis]

Closing a SerialTransport - for example pressing Ctrl-C on yakut monitor or yakut subscribe over a serial port - reliably prints an error traceback from the reader thread on macOS/POSIX, ending in:

Exception in thread Thread-1 (_reader_thread_func):
...
  File ".../pycyphal/transport/serial/_serial.py", line 455, in _reader_thread_func
    self._serial_port.close()
  File ".../serial/serialposix.py", line 533, in close
    os.close(self.fd)
OSError: [Errno 9] Bad file descriptor

To fix it, wrap the reader-thread close in try/except and ignore the error.

Reproduced on macOS, pycyphal 1.27.0, pyserial 3.5, Python 3.12, Cyphal/serial over a USB-UART adapter.

[coveralls]

coverage: 93.394%. remained the same — kristkis:master-v1 into OpenCyphal:master-v1

[pavel-kirienko]

Thanks! Please bump the patch version number in __init__.py

[kristkis]

Bumped to 1.27.1, thanks!