fix decompression indexing

Author: ChrisRackauckas

src/differentiation/compute_jacobian_ad.jl

@@ -108,8 +108,8 @@ function forwarddiff_color_jacobian!(J::AbstractMatrix{<:Number},
             rows_index, cols_index = ArrayInterface.findstructralnz(sparsity)
             for j in 1:chunksize
                 dx .= partials.(fx, j)
-                if ArrayInterface.fast_scalar_indexing(x1)
-                    for k in eachindex(cols_index)
+                if ArrayInterface.fast_scalar_indexing(dx)
+                    for k in 1:length(cols_index)
                         if color[cols_index[k]] == color_i
                             if J isa SparseMatrixCSC
                                 J.nzval[k] = dx[rows_index[k]]