feat(event): add filter query notes

Author: zeusoo001

framework/src/main/java/org/tron/core/services/jsonrpc/filters/LogMatch.java

@@ -85,6 +85,8 @@ public LogFilterElement[] matchBlockOneByOne()
     for (long blockNum : blockNumList) {
       List<TransactionInfo> transactionInfoList =
               manager.getTransactionInfoByBlockNum(blockNum).getTransactionInfoList();
+      //if query condition (address and topics) is empty, we will traversal every block,
+      //include empty block
       if (transactionInfoList.isEmpty()) {
         continue;
       }