nichemodel function generates too many links

[szefer-piotr]

Expected behavior

• nichemodel(85, 227) should produce networks with average number of links equal to 227

Actual behavior

• average number of links is ~ 2 * 227

Steps to reproduce

using EcologicalNetworks

mean_link = []
for iter in range(1,10000)
    sm = sum(nichemodel(85, 227))
    push!(mean_link, sm)
end
println(mean(mean_link))