Missing method definitions for column views

When using column views of sparse matrices, `sparse_view*dense` matrix multiplication works well, but `sparse_view*sparse` does not. I suspect this is an oversight and that it would be easy to make it work. Is that right? Here's an example. ```julia-repl julia> S = sparse(1:4, 1:4, 1:4) 4×4 SparseMatrixCSC{Int64, Int64} with 4 stored entries: 1 ⋅ ⋅ ⋅ ⋅ 2 ⋅ ⋅ ⋅ ⋅ 3 ⋅ ⋅ ⋅ ⋅ 4 julia> Sv = @view S[:,1:2] 4×2 view(::SparseMatrixCSC{Int64, Int64}, :, 1:2) with eltype Int64: 1 ⋅ ⋅ 2 ⋅ ⋅ ⋅ ⋅ julia> Sv*zeros(2) 4-element Vector{Float64}: 0.0 0.0 0.0 0.0 julia> Sv*spzeros(2) ERROR: MethodError: no method matching indtype(::SubArray{Int64, 2, SparseMatrixCSC{Int64, Int64}, Tuple{Base.Slice{Base.OneTo{…}}, UnitRange{Int64}}, false}) The function `indtype` exists, but no method is defined for this combination of argument types. ```