unhelpful bug messages

hey ! I get the following error :
TypeError: Vw is undefined

I am 100% sure its because I set up the convnet for regression incorrectly since if I try the example given in the getting started it works fine.

var layer_defs = [];
layer_defs.push({type:'input', out_sx:1, out_sy:1, out_depth:2});
layer_defs.push({type:'fc', num_neurons:5, activation:'sigmoid'});
layer_defs.push({type:'regression', num_neurons:1});
var net = new convnetjs.Net();
net.makeLayers(layer_defs);

var x11 = new convnetjs.Vol([1,2,3,4,5,6]);

// train on this datapoint, saying [0.5, -1.3] should map to value 0.7:
// note that in this case we are passing it a list, because in general
// we may want to regress multiple outputs and in this special case we
// used num_neurons:1 for the regression to only regress one.
var trainer = new convnetjs.SGDTrainer(net,
{learning_rate:0.01, momentum:0.0, batch_size:1, l2_decay:0.001});
trainer.train(x11, [1,2,3,4,5,6]);

This raises that error. So knowing js something is breaking and thus Vw becomes undefined. I'll try and go through the docs more carefully to understand how to set up. I am interested in regressing pairs of the form (xi, yi ) and thus why I set it up as it is seen...