make the server not send chunks redundantly when there aren't any to send

crates/rkgk/src/api/wall.rs

@@ -429,6 +429,7 @@ impl SessionLoop {
             }
         }
 
+        if !chunk_infos.is_empty() {
             ws.send(to_message(&Notify::Chunks {
                 chunks: chunk_infos,
                 has_more: !self.pending_images.is_empty()
@@ -436,6 +437,7 @@ impl SessionLoop {
             }))
             .await?;
             ws.send(Message::Binary(packet)).await?;
+        }
 
         Ok(())
     }