message: fixes guard use in non-member function
diff: @@ -567,7 +567,7 @@ void cusparse_generic_spmv(std::shared_ptr<const gko::CudaExecutor> gpu_exec,
  auto dense_x = gko::as<gko::matrix::Dense<ValueType>>(x);
  auto db = dense_b->get_const_values();
  auto dx = dense_x->get_values();
  - auto guard = this->get_gpu_exec()->get_scoped_device_id_guard();
  + auto guard = gpu_exec->get_scoped_device_id_guard();
  cusparseDnVecDescr_t vecb, vecx;
  GKO_ASSERT_NO_CUSPARSE_ERRORS(
  cusparseCreateDnVec(&vecx, dense_x->get_num_stored_elements(),
  