Kolibri public contentnode API sometimes returns JSON string for `options`

[bjester]

Observed behavior

Sometimes options is a JSON string and not an object:
https://hotfixes.studio.learningequality.org/api/public/v2/contentnode/b9c2516c24585465984650b76d0e820a/

Expected behavior

It shouldn't be a JSON string, like sometimes it isn't:
https://hotfixes.studio.learningequality.org/api/public/v2/contentnode/9c31e431d0454e42bb577457b61f16a2/

[rtibbles]

Fixed in #4146