address PR comment

crates/sui-bridge-indexer/src/sui_transaction_handler.rs

@@ -37,7 +37,6 @@ pub async fn handle_sui_transactions_loop(
     while let Some(batch) = stream.next().await {
         // unwrap: batch must not be empty
         let (txns, cursor) = batch.last().cloned().unwrap();
-        let last_ckp = txns.last().map(|tx| tx.checkpoint).unwrap_or_default();
         let token_transfers = batch
             .into_iter()
             // TODO: letting it panic so we can capture errors, but we should handle this more gracefully
@@ -46,6 +45,7 @@ pub async fn handle_sui_transactions_loop(
 
         // write batched token transfers to DB
         if !token_transfers.is_empty() {
+            let last_ckp = txns.last().map(|tx| tx.checkpoint).unwrap_or_default();
             // unwrap: token_transfers is not empty
             while let Err(err) = write(&pg_pool, token_transfers.clone()) {
                 error!("Failed to write sui transactions to DB: {:?}", err);