GSA BoundsError when the range of the first parameter is a single value

[natema]

Let's consider the example for using Morris method in the tutorial :

using GlobalSensitivity, Statistics, OrdinaryDiffEq, QuasiMonteCarlo

function f(du,u,p,t)
  du[1] = p[1]*u[1] - p[2]*u[1]*u[2] #prey
  du[2] = -p[3]*u[2] + p[4]*u[1]*u[2] #predator
end
u0 = [1.0;1.0]
tspan = (0.0,10.0)
p = [1.5,1.0,3.0,1.0]
prob = ODEProblem(f,u0,tspan,p)
t = collect(range(0, stop=10, length=200))
f1 = function(p)
    prob1 = remake(prob;p=p)
    sol = solve(prob1,Tsit5();saveat=t)
    [mean(sol[1,:])]
end

m = gsa(f1,Morris(total_num_trajectory=1000,num_trajectory=150),[[1,5],[1,5],[1,5],[1,5]]

The example works fine if we change the range of some parameters to consist of a single point (e.g. [[1,5],[1,1],[1,1],[1,5]] for the second and third parameters), but raises an error if we do that for the first parameter:

julia> m = gsa(f1,Morris(total_num_trajectory=1000,num_trajectory=150),[[1,1],[1,5],[1,5],[1,5]])
ERROR: BoundsError: attempt to access 0-element Vector{Vector{Float64}} at index [1]
Stacktrace:
 [1] getindex(A::Vector{Vector{Float64}}, i1::Int64)
   @ Base ./essentials.jl:13
 [2] gsa(f::var"#9#10", method::Morris, p_range::Vector{Vector{…}}; batch::Bool, rng::Random.TaskLocalRNG, kwargs::@Kwargs{})
   @ GlobalSensitivity ~/.julia/packages/GlobalSensitivity/SJGNh/src/morris_sensitivity.jl:213
 [3] gsa(f::Function, method::Morris, p_range::Vector{Vector{Int64}})
   @ GlobalSensitivity ~/.julia/packages/GlobalSensitivity/SJGNh/src/morris_sensitivity.jl:135
 [4] top-level scope
   @ REPL[2]:1
Some type information was truncated. Use `show(err)` to see complete types.