In JSON card_history always empty

[griago]

After long time, I extracted again the JSON and I noticed that the card_history field is always empty.

Is this a bug?

Here is an example.

{"history":[{"id":44661886,"mode":"ranked","hero":"Shaman","hero_deck":"Midrange","opponent":"Warlock","opponent_deck":"Zoo","coin":false,"result":"win","duration":336,"note":null,"added":"2016-10-09T09:35:30.000Z","card_history":[],"rank":20,"legend":null},{"id":44661216,"mode":"ranked","hero":"Shaman","hero_deck":"Midrange","opponent":"Warlock","opponent_deck":"Reno","coin":true,"result":"win","duration":778,"note":null,"added":"2016-10-09T09:29:42.000Z","card_history":[],"rank":20,"legend":null},{"id":44659842,"mode":"ranked","hero":"Shaman","hero_deck":"Midrange","opponent":"Warrior","opponent_deck":"Dragon","coin":true,"result":"loss","duration":624,"note":null,"added":"2016-10-09T09:16:32.000Z","card_history":[],"rank":20,"legend":null},{"id":44589983,"mode":"ranked","hero":"Warlock","hero_deck":"Zoo","opponent":"Mage","opponent_deck":"Tempo","coin":false,"result":"win","duration":859,"note":null,"added":"2016-10-08T17:32:39.000Z","card_history":[],"rank":20,"legend":null},{"id":44587962,"mode":"ranked","hero":"Warlock","hero_deck":"Zoo","opponent":"Warlock","opponent_deck":"Reno","coin":true,"result":"loss","duration":525,"note":null,"added":"2016-10-08T17:18:04.000Z","card_history":[],"rank":20,"legend":null},{"id":44563502,"mode":"ranked","hero":"Warlock","hero_deck":"Zoo","opponent":"Warrior","opponent_deck":"C'Thun","coin":false,"result":"win","duration":790,"note":null,"added":"2016-10-08T14:09:56.000Z","card_history":[],"rank":20,"legend":null},{"id":44561624,"mode":"ranked","hero":"Priest","hero_deck":"Control","opponent":"Hunter","opponent_deck":"Midrange","coin":false,"result":"loss","duration":459,"note":null,"added":"2016-10-08T13:55:20.000Z","card_history":[],"rank":20,"legend":null},{"id":44319588,"mode":"ranked","hero":"Priest","hero_deck":null,"opponent":"Mage","opponent_deck":null,"coin":false,"result":"loss","duration":1052,"note":null,"added":"2016-10-06T15:04:50.000Z","card_history":[],"rank":20,"legend":null},{"id":44317531,"mode":"ranked","hero":"Priest","hero_deck":null,"opponent":"Druid","opponent_deck":"Token","coin":true,"result":"loss","duration":480,"note":null,"added":"2016-10-06T14:47:10.000Z","card_history":[],"rank":20,"legend":null},{"id":43952798,"mode":"ranked","hero":"Mage","hero_deck":"Tempo","opponent":"Priest","opponent_deck":"C'Thun","coin":true,"result":"win","duration":679,"note":null,"added":"2016-10-03T16:50:37.000Z","card_history":[],"rank":20,"legend":null},{"id":43830823,"mode":"ranked","hero":"Druid","hero_deck":"C'Thun","opponent":"Priest","opponent_deck":null,"coin":false,"result":"win","duration":629,"note":null,"added":"2016-10-02T17:29:25.000Z","card_history":[],"rank":21,"legend":null},{"id":43829315,"mode":"ranked","hero":"Druid","hero_deck":"C'Thun","opponent":"Hunter","opponent_deck":"Midrange","coin":true,"result":"win","duration":353,"note":null,"added":"2016-10-02T17:18:50.000Z","card_history":[],"rank":21,"legend":null},{"id":43826244,"mode":"ranked","hero":"Druid","hero_deck":"C'Thun","opponent":"Paladin","opponent_deck":null,"coin":true,"result":"loss","duration":748,"note":null,"added":"2016-10-02T16:56:59.000Z","card_history":[],"rank":21,"legend":null},{"id":43770762,"mode":"ranked","hero":"Druid","hero_deck":"C'Thun","opponent":"Warlock","opponent_deck":null,"coin":false,"result":"win","duration":351,"note":null,"added":"2016-10-02T09:24:01.000Z","card_history":[],"rank":22,"legend":null},{"id":43770177,"mode":"ranked","hero":"Druid","hero_deck":null,"opponent":"Warrior","opponent_deck":"C'Thun","coin":false,"result":"loss","duration":786,"note":null,"added":"2016-10-02T09:17:57.000Z","card_history":[],"rank":22,"legend":null}],"meta":{"current_page":1,"next_page":2,"prev_page":null,"total_pages":32,"total_items":480}}