`getindex(vi::UntypedVarInfo, spl::AbstractSampler)` fails

[penelopeysm]

Currently, this dispatches to:

DynamicPPL.jl/src/varinfo.jl

Line 1697 in 18af48a

getindex(vi::VarInfo, spl::Sampler) = copy(getindex_internal(vi, _getranges(vi, spl)))

In the case of vi::UntypedVarInfo, _getranges(vi, spl) returns a boring old Vector{Int64}, but there is no method for getindex_internal that can handle that.

This causes the test failures on test/turing/varinfo.jl seen here https://github.com/TuringLang/DynamicPPL.jl/actions/runs/11579951675/job/32237371466