unset on the higher leve item fails

[cooolbasha]

Hi,
if there is a model with fields
model =
name: 'test'
kart:
r1: [4,4,o]
r2:[8,8]
if I call model.unset('kart') ..it does update the model. but the model changes does not trigger to model binder..if it is done 1 at a time say model.unset('kart.r1') works