message: Update data_reader.hpp and fix debug mode compile time error
diff: @@ -168,8 +168,6 @@ DataReader<TypeKey>::DataReader(int batchsize, size_t label_dim,
  csr_heap_.reset(new HeapEx<CSRChunk<TypeKey>>(num_chunk_threads, total_gpu_count, batchsize_,
  label_dim_ + dense_dim_, params_));
  - assert(data_readers_.empty() && data_reader_threads_.empty());
  -
  const auto& device_list = device_resources_->get_device_list();
  