expecting None response on @process_api_key_and_nonce

[karamelniycoder]

ret can be None if any errors occurs, for example with error «TriggerPrice is invalid» on creating order.
cuz ret.code raising 'NoneType' object has no attribute 'code'

created_tx, ret, err = await func(self, *args, **kwargs, nonce=nonce, api_key_index=api_key_index)
if ret.code != CODE_OK:
   ^^^^^^^^

now we checking value of ret as in any other code

created_tx, ret, err = await func(self, *args, **kwargs, nonce=nonce, api_key_index=api_key_index)
if (ret is None and err) or (ret and ret.code != CODE_OK):