Garrett Smith

Fix error TuringOptimExt.jl with information matrix/vcov

2

I've been using the MLE/MAP estimation functionality ([defined here](https://github.com/TuringLang/Turing.jl/blob/master/ext/TuringOptimExt.jl)) with some Turing models, and I've come across an error in the `informationmatrix` function, extended from StatsBase. In the function definition,...