Interpolation bug when calling without extrapolate

I am using Interpolations.jl v0.14.7 (because another low level package KernelDensity has not updated its compatibility).

```julia
julia> using Interpolations

julia> itp0 = interpolate([1, 2, 3, 4], BSpline(Linear()))
4-element interpolate(::Vector{Float64}, BSpline(Linear())) with element type Float64:
Error showing value of type Interpolations.BSplineInterpolation{Float64, 1, Vector{Float64}, BSpline{Linear{Throw{OnGrid}}}, Tuple{Base.OneTo{Int64}}}:
ERROR: BoundsError: attempt to access Tuple{} at index [1]
Stacktrace:
[1] getindex(t::Tuple, i::Int64)
@ Base .\tuple.jl:31
[2] _checklubounds(tf::Bool, ls::Tuple{}, us::Tuple{}, xs::Tuple{Int64})
@ Interpolations C:\Users\hyzho\.julia\packages\Interpolations\nDwIa\src\Interpolations.jl:420
```

However the following is fine:

```julia
etp = extrapolate(interpolate([1,2,3,4], BSpline(Linear())), Periodic())
```

I found this while reading the documentation on [periodic extrapolation](https://juliamath.github.io/Interpolations.jl/stable/extrapolation/#Periodic-extrapolation).