added error handling for the case when msg was not able to extracted from tx during throttling tx

node/worker/worker.go

@@ -128,9 +128,12 @@ func (w *Worker) SelectTransactionsForNewBlock(newBlockNum uint64, txs types.Tra
 
 			} else {
 				selected = append(selected, tx)
+				// handle the case when msg was not able to extracted from tx
+				if len(sender.String()) > 0 {
 					recentTxsStats[newBlockNum][sender]++
 				}
 			}
+		}
 
 		// log invalid or unselected txs
 		if flag == shardingconfig.TxUnselect || flag == shardingconfig.TxInvalid {