delete sign value

sdk/auth/rpc_signature_composer.go

@@ -86,7 +86,7 @@ func unsignRpcRequest(request *http.Request, signer Signer) (err error) {
 	}
 
 	if accessKey, err := signer.GetAccessKeyId(); err != nil {
-		return
+		return err
 	} else if accessKey == "" {
 		return errors.New("access key is not allow empty")
 	} else if accessKey != signParams["access_key"] {