A simplification...

gistfile1.txt

app.post('/images'
  , function(req, res, next) {
      var form = formidable.IncomingForm();
      form.parse(req, function(err, fields, files) {
        console.log('__err__', err);                      // err === [Error: Request aborted]
        console.log('__fields__', fields);                // fields === {}
        console.log('__files__', files);                  // files === {}
        next();
      });
    }
  , _addImages
);

function _addImages(req, res, next) {
  // This point is never reached.
}