Update src/config.jl

Author: ChrisRackauckas

src/config.jl

@@ -238,8 +238,8 @@ This constructor does not store/modify `y` or `x`.
 function JacobianConfig(f::F,
                         y::AbstractArray{Y},
                         x::AbstractArray{X},
-                        ::Chunk{N},
-                        ::T) where {F,Y,X,N,T}
+                        ::Chunk{N} = Chunk(x),
+                        ::T = Tag(f, X)) where {F,Y,X,N,T}
     seeds = construct_seeds(Partials{N,X})
     yduals = similar(y, Dual{T,Y,N})
     xduals = similar(x, Dual{T,X,N})