Thanks for the clarification.
You’re correct about parsing the empty string, I made an assumption that if parsing doesn’t error then the result would have the “chatters” object, and arrays for each type of users, which would be concatenated to a full list of users and it was this that was throwing the error when “chatters” was undefined and being caught by the same thing I had catching JSON parse errors. I didn’t expect to encounter the situation where the parse would complete but not contain those objects/arrays.