Opaque field with zero length serialized as one byte

[senier]

The following message has an opaque field which may have a size of zero:

package Test is
   type Length is mod 2**8;
   type M is
      message
         Length : Length
            then Data
               with Size => 8 * Length;
         Data : Opaque;
      end message;
end Test;

When serializing a message where Length is zero, the Data field is serialized as a single byte with value 0:

data = b"\x00"

msg = PyRFLX.from_specs (["test.rflx"], skip_model_verification=True)["Test"]["M"]
msg.parse (data)                                                                                                    

if data != msg.bytestring:
    print(f"Serialization mismatch:\ngot:      {msg.bytestring.hex()}\nexpected: {data.hex()}")

$ ./parse.py                                       
Serialization mismatch:
got:      0000
expected: 00