Mapquest fails to wake the watchdog

When using mapquest, if for some reason the request fails, mapquest returns a plain text string (or did in my case). The string is a verbose error message.

Code says in geocoder/plugins/geocoder_handler/mapquest_nominatim.inc

if (!isset($data[0]->lon)) {
    return NULL;
  }

and so the request fails without an error message.

(as a side remark: the error message is about the api key I entered in the settings. the key is ok .. but there is also a secret .. has mapquest recently changed its apis?)