* BUG SYMPTOM: some send response handlers error when they try to
  destructure a null `data` field
* CAUSE: the `{identityFailure}` destructuring assignment unsafely
  assumes that all `send_message` values will have a `data` field on
  which we can call `data[0]`
* FIX: don't assume anything about the shape of the `data`
  field. extract `identityFailure` from it (if it is there) with a
  lodash `get` call to the full path to the field we are trying
  to (conditionally) extract