fix(users): Fix a bug where error parsing causes user blocking to not function properly

In a previous MR, we updated the user block to not have hard-coded error messages that were confusing things. However, as part of that, we parsed the body into an error JSON. A successful block only returns true in the body, though, which failed to parse into JSON.

This caused our release-1.0 integration tests to fail when merging, but since this bug was injected in a 0.X release, I've opened a bugfix against 0.X so that users who haven't consumed 1.0 can get the fix.