For checking if a stream is live or not, the best endpoint would be the /streams/:CHANNEL endpoint. For this one, you can just check if the stream object is null or contains any values. If user is streaming, the stream object will have multiple values (including mature and viewer count) whereas if user is not streaming, the entire object will just be null. Stepping into the stream object to check an additional value is a needless step (unless you have a secondary purpose for checking that specific value.)
Ex. Offline user
{“stream”:null,“_links”:{“self”:“https://api.twitch.tv/kraken/streams/dansgaming",“channel”:"https://api.twitch.tv/kraken/channels/dansgaming”}}