It appears as though there is little info for streams if the user is not currently live streaming. For example, I simply typed in the api call into the browser for OgamingSC2 [https://wind-bow.glitch.me/twitch-api/streams/OgamingSC2] and got this as a response:
{"stream":{"_id":26119435280,"game":"StarCraft II","viewers":192,"video_height":720,"average_fps":60.0282485876,"delay":0,"created_at":"2017-08-27T21:01:40Z","is_playlist":false,"stream_type":"live","preview":{"small":"https://static-cdn.jtvnw.net/previews-ttv/live_user_ogamingsc2-80x45.jpg","medium":"https://static-cdn.jtvnw.net/previews-ttv/live_user_ogamingsc2-320x180.jpg","large":"https://static-cdn.jtvnw.net/previews-ttv/live_user_ogamingsc2-640x360.jpg","template":"https://static-cdn.jtvnw.net/previews-ttv/live_user_ogamingsc2-{width}x{height}.jpg"},"channel":{"mature":false,"partner":false,"status":"MASTER'S COLISEUM 2017","broadcaster_language":"fr","display_name":"OgamingSC2","game":"StarCraft II","language":"fr","_id":71852806,"name":"ogamingsc2","created_at":"2014-09-24T15:06:58Z","updated_at":"2017-08-28T02:34:50Z","delay":null,"logo":"https://static-cdn.jtvnw.net/jtv_user_pictures/ogamingsc2-profile_image-9021dccf9399929e-300x300.jpeg","banner":null,"video_banner":"https://static-cdn.jtvnw.net/jtv_user_pictures/ogamingsc2-channel_offline_image-1570cf4930177aa3-1920x1080.jpeg","background":null,"profile_banner":"https://static-cdn.jtvnw.net/jtv_user_pictures/ogamingsc2-profile_banner-d418aed2c0ef7d35-480.jpeg","profile_banner_background_color":"","url":"https://www.twitch.tv/ogamingsc2","views":27741071,"followers":58050,"_links":{"self":"https://api.twitch.tv/kraken/channels/ogamingsc2","follows":"https://api.twitch.tv/kraken/channels/ogamingsc2/follows","commercial":"https://api.twitch.tv/kraken/channels/ogamingsc2/commercial","stream_key":"https://api.twitch.tv/kraken/channels/ogamingsc2/stream_key","chat":"https://api.twitch.tv/kraken/chat/ogamingsc2","features":"https://api.twitch.tv/kraken/channels/ogamingsc2/features","subscriptions":"https://api.twitch.tv/kraken/channels/ogamingsc2/subscriptions","editors":"https://api.twitch.tv/kraken/channels/ogamingsc2/editors","teams":"https://api.twitch.tv/kraken/channels/ogamingsc2/teams","videos":"https://api.twitch.tv/kraken/channels/ogamingsc2/videos"}},"_links":{"self":"https://api.twitch.tv/kraken/streams/ogamingsc2"}},"_links":{"self":"https://api.twitch.tv/kraken/streams/Ogamingsc2","channel":"https://api.twitch.tv/kraken/channels/Ogamingsc2"}}
Meanwhile, I got this for storbeck [https://wind-bow.glitch.me/twitch-api/streams/storbeck]:
{"stream":null,"_links":{"self":"https://api.twitch.tv/kraken/streams/storbeck","channel":"https://api.twitch.tv/kraken/channels/storbeck"}}
Judging by the API requests Root Domain URL, it is using some third-party service on top of Twitch’s main API - more than likely to keep things simple for the sake of the tutorial. (https://wind-bow.glitch.me is not associated directly with Twitch. - The native Twitch API is api.twitch.tv as the root domain.)
Otherwise, you would have to sign up for a Twitch account and request a developer key to get access to the API.
Long story short, it’s nothing wrong with your code - the third-party API call is not returning the full amount of info for all users.
Hope that helps.