Fix dist compile error (#8987)

Author: Yancey

paddle/fluid/operators/detail/bytebuffer_stream.cc

@@ -85,4 +85,4 @@ google::protobuf::int64 GrpcByteBufferSource::ByteCount() const {
 
 }  // namespace detail
 }  // namespace operators
-}  // namespace paddle
+}  // namespace paddle

paddle/fluid/operators/detail/sendrecvop_utils.cc

@@ -82,7 +82,7 @@ void SerializeToByteBuffer(const std::string& name, framework::Variable* var,
   DestroyCallback destroy_callback = [](void* backing) {};
 
   void* buf = malloc(1024);
-  void* payload;
+  void* payload = nullptr;
   size_t payload_size;
   ProtoEncodeHelper e((char*)buf, 1024);
   e.WriteString(VarMsg::kVarnameFieldNumber, name);
@@ -297,4 +297,4 @@ void DeserializeFromByteBuffer(const ::grpc::ByteBuffer& msg,
 
 }  // namespace detail
 }  // namespace operators
-}  // namespace paddle
+}  // namespace paddle