What the allowed SOKS5A error responses?

[dimaqq]

Ref: tailscale/tailscale#6144

that particular project set up a local SOCKS5A server, which sometimes responds, on upstream error, in a way that this Python client library doesn't like, which yields this backtrace:

python3.10/site-packages/socksio/socks5.py", line 257, in loads
    atype = SOCKS5AType(data[3:4])
  File "/usr/local/lib/python3.10/enum.py", line 385, in __call__
    return cls.__new__(cls, value)
  File "/usr/local/lib/python3.10/enum.py", line 710, in __new__
    raise ve_exc
ValueError: b'\x00' is not a valid SOCKS5AType

Thus the question, if the server somehow rejects the request, is it required to fill in bind address type, address and port, or can those be left blank (zero) if the reply (code) is not zero?