message: fix empty kernel launch in COO SpMV
diff: @@ -114,7 +114,7 @@ void spmv2(std::shared_ptr<const CudaExecutor> exec,
  const dim3 coo_block(config::warp_size, warps_in_block, 1);
  const auto nwarps = host_kernel::calculate_nwarps(exec, nnz);
  - if (nwarps > 0) {
  + if (nwarps > 0 && b_ncols > 0) {
  if (b_ncols < 4) {
  const dim3 coo_grid(ceildiv(nwarps, warps_in_block), b_ncols);
  int num_lines = ceildiv(nnz, nwarps * config::warp_size);
  @@ -152,7 +152,7 @@ void advanced_spmv2(std::shared_ptr<const CudaExecutor> exec,
  const dim3 coo_block(config::warp_size, warps_in_block, 1);
  const auto b_ncols = b->get_size()[1];
  - if (nwarps > 0) {
  + if (nwarps > 0 && b_ncols > 0) {
  if (b_ncols < 4) {
  int num_lines = ceildiv(nnz, nwarps * config::warp_size);
  const dim3 coo_grid(ceildiv(nwarps, warps_in_block), b_ncols);
  