message: ffi missing error code
diff: @@ -58,6 +58,7 @@ impl From<SignerError> for ffi_support::ExternError {
  SignerError::InvalidBIP44Path(_) => 8,
  SignerError::TryFromSlice(_) => 10,
  SignerError::DecodeError(_) => 11,
  + SignerError::DeserializeError(_) => 12,
  };
  Self::new_error(ffi_support::ErrorCode::new(code), e.to_string())
  }
  