A nonlinear problem


I am a beginner of FreeFem.
I am studying how to solve nonlinear problems and make codes.
In reference to the examples provided by the FREEFEM guidebook, I am trying to use the Newton method.

My problem is f= - div(|grad(u)|^2 * grad(u)) .
My goal is to make codes for FEM and DGM.
I think that the code for FEM I wrote is fine but the code for DGM has problems.
Probably, I do not understand how to differentiate weak formulae.

I have an error on the line below.
intalledges(Th) ( mode*( jump(u)mean(2(dx(u)*dx(du)+dy(u)*dy(du))*dn(v)) )/nTonEdge )

Could you tell me why it causes an error. I do not understand the error message.

Thank you