unconstrained denominators in computed_batched_barycentric_evaluations function

[DanielKotov]

There is a problem in function "compute_batched_barycentric_evaluations" in file small_subgroup_ipa.hpp.

The point is elements of vector denominators are multiplied with coefficients of challenge polynomial. Coefficients of challenge polynomial(challenge_polynomial_lagrange) are computed in function compute_challenge_polynomial_coeffs in file small_subgroup_ipa.hpp. However, because of incorrect initialization of vector of result variables, some variables still constant and have addition_constant = 0 and multiplication_constant =1 and there won't be gates which constrain denominators.

As you can see here, some elements of a challenge_polynomial_lagrange are constant which leads to absence of some constraints.