Elliptic fibration book example errors

[joschmitt]

The book example in the file specialized/brandhorst-zach-fibration-hopping/vinberg_3.jlcon errors both on OSCAR 1.1 and current master:

julia> K = QQ;

julia> Kt, t = polynomial_ring(K, :t);

julia> Ktf = fraction_field(Kt);

julia> E = elliptic_curve(Ktf, [0, -t^3, 0, t^3, 0]);

julia> P = E([t^3, t^3]);

julia> Y2 = elliptic_surface(E, 2, [P]);

julia> S = weierstrass_model(Y2)[1];

julia> basisNSY2, _, NSY2 = algebraic_lattice(Y2);

julia> fibers_in_Y2 = [QQ.(vec(collect(i))) for i in [
        [4   2   0   0   0   0   0   0   0   -4   -4   -8   -7   -6   -5   -4   -3   -2   -1   0],
        [1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0],
        [5   2   -2   -3   -4   -3   -2   -1   -2   -5   -4   -8   -7   -6   -5   -4   -3   -2   -1   0],
        [4   2   -2   -4   -6   -9//2   -3   -3//2   -7//2   -3   -5//2   -5   -9//2   -4   -7//2   -3   -5//2   -2   -3//2   0],
        [2   1   -1   -2   -3   -2   -1   0   -2   -1   -1   -2   -2   -2   -2   -2   -2   -1   0   1],
        [2   1   0   0   0   0   0   0   0   -2   -2   -4   -4   -4   -4   -3   -2   -1   0   1]
       ]];

julia> @assert all(inner_product(ambient_space(NSY2), i,i) == 0 for i in fibers_in_Y2)

julia> [representative(elliptic_parameter(Y2, f)) for f in fibers_in_Y2[4:6]]
ERROR: AssertionError: found
Stacktrace:
 [1] horizontal_decomposition(X::EllipticSurface{QQField, AbstractAlgebra.Generic.FracFieldElem{…}}, F::Vector{QQFieldElem})
   @ Oscar ~/.julia/dev/Oscar/experimental/Schemes/src/elliptic_surface.jl:1349
 [2] elliptic_parameter(X::EllipticSurface{QQField, AbstractAlgebra.Generic.FracFieldElem{…}}, F::Vector{QQFieldElem})
   @ Oscar ~/.julia/dev/Oscar/experimental/Schemes/src/elliptic_surface.jl:1419
 [3] (::var"#5#6")(f::Vector{QQFieldElem})
   @ Main ./none:0
 [4] iterate
   @ ./generator.jl:47 [inlined]
 [5] collect(itr::Base.Generator{Vector{Vector{QQFieldElem}}, var"#5#6"})
   @ Base ./array.jl:834
 [6] top-level scope
   @ REPL[12]:1
Some type information was truncated. Use `show(err)` to see complete types.

Notice that this is one of the examples that is not run by CI. (The code above runs for a few minutes.)