getRules is better to return {empty: true} for empty rules

[tlyau62]

For the getRules api, the returned rules array may be better to have the empty rule like the following

{
  "empty": true
}

instead of the null values object to prevent ambiguity.

{
  "id": null,
  "filter": null,
  "value": null
  // ...
}

So, may we have an option like this which also support for backward compatibility?

builder.getRules({
  "emptyRule": true
})

[mistic100]

if filter is null then then rule is empty, and the rule is only considered empty if the filter is null

you can also already ignore empty rules with skip_empty option

no need for change