Evaluating at endpoints of open interval

The code seems to be creating errors by trying to evaluate at endpoints of an open interval, when the function might not exist at these endpoints:

julia> d
(0.0..3.0 (open)) × (0.0..10.0 (open))

julia> f = Fun((ξ, σ) -> log_posterior(data, ξ, σ), d)
ERROR: ArgumentError: GeneralizedPareto: the condition σ > zero(σ) is not satisfied.
Stacktrace:
  [1] macro expansion
    @ ~/.julia/packages/Distributions/vR2pk/src/utils.jl:6 [inlined]
  [2] #GeneralizedPareto#147
    @ ~/.julia/packages/Distributions/vR2pk/src/univariate/continuous/generalizedpareto.jl:41 [inlined]
  [3] GeneralizedPareto
    @ ~/.julia/packages/Distributions/vR2pk/src/univariate/continuous/generalizedpareto.jl:41 [inlined]
  [4] GeneralizedPareto
    @ ~/.julia/packages/Distributions/vR2pk/src/univariate/continuous/generalizedpareto.jl:50 [inlined]
  [5] #9
    @ ./REPL[21]:1 [inlined]
  [6] mapreduce_impl(f::var"#9#10"{Float64, Float64}, op::typeof(Base.add_sum), A::Vector{Float64}, ifirst::Int64, ilast::Int64, blksize::Int64)
    @ Base ./reduce.jl:244
  [7] mapreduce_impl
    @ ./reduce.jl:259 [inlined]
  [8] _mapreduce(f::var"#9#10"{Float64, Float64}, op::typeof(Base.add_sum), #unused#::IndexLinear, A::Vector{Float64})
    @ Base ./reduce.jl:417
  [9] _mapreduce_dim
    @ ./reducedim.jl:330 [inlined]
 [10] #mapreduce#725
    @ ./reducedim.jl:322 [inlined]
 [11] mapreduce
    @ ./reducedim.jl:322 [inlined]
 [12] #_sum#735
    @ ./reducedim.jl:894 [inlined]
 [13] _sum
    @ ./reducedim.jl:894 [inlined]
 [14] #sum#733
    @ ./reducedim.jl:890 [inlined]
 [15] sum
    @ ./reducedim.jl:890 [inlined]
 [16] log_like
    @ ./REPL[21]:1 [inlined]
 [17] log_posterior(x::Vector{Float64}, ξ::Float64, σ::Float64)
    @ Main ./REPL[23]:1
 [18] (::var"#31#32")(ξ::Float64, σ::Float64)
    @ Main ./REPL[63]:1
 [19] (::ApproxFunBase.DFunction)(::Float64, ::Vararg{Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/LinearAlgebra/helper.jl:647
 [20] (::ApproxFunBase.var"#22#24"{ApproxFunBase.DFunction})(xy::StaticArrays.SVector{2, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:100
 [21] (::ApproxFunBase.DFunction)(args::StaticArrays.SVector{2, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/LinearAlgebra/helper.jl:647
 [22] _broadcast_getindex_evalf
    @ ./broadcast.jl:670 [inlined]
 [23] _broadcast_getindex
    @ ./broadcast.jl:643 [inlined]
 [24] getindex
    @ ./broadcast.jl:597 [inlined]
 [25] macro expansion
    @ ./broadcast.jl:961 [inlined]
 [26] macro expansion
    @ ./simdloop.jl:77 [inlined]
 [27] copyto!
    @ ./broadcast.jl:960 [inlined]
 [28] copyto!
    @ ./broadcast.jl:913 [inlined]
 [29] materialize!
    @ ./broadcast.jl:871 [inlined]
 [30] materialize!
    @ ./broadcast.jl:868 [inlined]
 [31] broadcast!(f::ApproxFunBase.DFunction, dest::Vector{Float64}, As::Vector{StaticArrays.SVector{2, Float64}})
    @ Base.Broadcast ./broadcast.jl:837
 [32] default_Fun(#unused#::Type{Float64}, f::Function, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64}, pts::Vector{StaticArrays.SVector{2, Float64}}, #unused#::Type{Val{false}})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:44
 [33] default_Fun(f::ApproxFunBase.DFunction, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64}, n::Int64, #unused#::Type{Val{false}})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:57
 [34] default_Fun(f::Function, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64}, n::Int64)
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:72
 [35] default_Fun(f::ApproxFunBase.DFunction, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:121
 [36] Fun(f::Function, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:177
 [37] default_Fun(f::ApproxFunBase.DFunction, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:100
 [38] Fun(f::Function, d::TensorSpace{Tuple{Chebyshev{OpenInterval{Float64}, Float64}, Chebyshev{OpenInterval{Float64}, Float64}}, VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}}, Float64})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:177
 [39] Fun(f::Function, d::VcatDomain{2, Float64, (1, 1), Tuple{OpenInterval{Float64}, OpenInterval{Float64}}})
    @ ApproxFunBase ~/.julia/packages/ApproxFunBase/vVgJc/src/constructors.jl:173
 [40] top-level scope
    @ REPL[63]:1

Reproduce the Julia example with Fun on the two-dimensional open interval and follow the ApproxFunBase entry points shown in the stack trace, especially default_Fun and constructors.jl. Determine whether endpoint samples are being generated despite the open domains; done should be demonstrated by the example no longer evaluating the invalid endpoint values without breaking valid open-interval construction.