Estimation of order sorted norms returns `nan` when zero is expected

[afossa]

As per documentation, DA.estimNorm() should return zero for each order sorted norm if estimation is not possible (e.g. there are less than two non-constant coefficients which are not zero).

However, calling this method on a polynomial with a single non-zero coefficient of order >0 returns a vector of nan.

This is due to the fact that that linear regression in daceEstimate is still attempted, even if a warning is thrown to inform that there is not enough data to perform it.