message: schema: support empty QueryMsg in QueryResponses
diff: @@ -50,10 +50,8 @@ fn check_api_integrity<T: QueryResponses + ?Sized>(
  // something more readable below?
  - let schema_queries: BTreeSet<_> = schema
  - .schema
  - .subschemas
  - .ok_or(IntegrityError::InvalidQueryMsgSchema)?
  + let schema_queries: BTreeSet<_> = match schema.schema.subschemas {
  + Some(subschemas) => subschemas
  .one_of
  .ok_or(IntegrityError::InvalidQueryMsgSchema)?
  .into_iter()
  @@ -66,7 +64,10 @@ fn check_api_integrity<T: QueryResponses + ?Sized>(
  .next()
  .ok_or(IntegrityError::InvalidQueryMsgSchema)
  })
  - .collect::<Result<_, _>>()?;
  + .collect::<Result<_, _>>()?,
  + None => BTreeSet::new(),
  + };
  +
  if schema_queries != generated_queries {
  return Err(IntegrityError::InconsistentQueries {
  query_msg: schema_queries,
  