facebook js sdk notification callback response changes?

Question

Just a quick question to make sure i'm on track - I've started supporting a ready FB app. Yesterday the client reported an issue with a part of the app which uses the fb JS SDK notification plugin. In the callback the code refers to (this is only the callback of the entire FB.io):

}, function(res) {
                if(typeof(res)!='undefined' && res != null){ // if user invited friends
                        var ids = res.request_ids.toString();

but when I console.log the res object, there is no res.request_ids - onlt res.request and res.to (which contains the IDs).

Can it be that Facebook changed the response object? I could find the official docs which say that i'm correct about the object - there are 'request' and 'to' properties, no request_ids - but why would it work till now? was there a change in the response object? is there a place where these changes are published in advance in order to prevent downtime? Thanks...