FileFormats.NL does not support univariate OPMULT

[odow]

From discourse: https://discourse.julialang.org/t/bad-line-xxx-of-yyy-nl-file-error-with-amplnlwriter-but-solves-with-ipopt-jl/82372

using JuMP
import AmplNLWriter
import Ipopt_jll

function main()
    model = Model(() -> AmplNLWriter.Optimizer(Ipopt_jll.amplexe))
    @variable(model, x)
    @NLobjective(model, Min, prod(x for j=1:1))
    optimize!(model)
    return
end

main()

# g3 1 1 0
#  1 0 1 0 0 0
#  0 1
#  0 0
#  0 1 0
#  0 0 0 1
#  0 0 0 0 0
#  0 1
#  0 0
#  0 0 0 0 0
# O0 0
# o2    # OPMULT        <-- expects two arguments
# v0    # variable "x"
# x1
# 0 0
# b
# 3
# G0 1
# 0 0