From cc4f314b967235e722a0e484bc4e5c6436fe028e Mon Sep 17 00:00:00 2001
From: Michael Zhou <zhoumotongxue008@gmail.com>
Date: Sat, 18 Oct 2025 09:43:17 -1000
Subject: [PATCH] Use empty array instead of nil for topics

Fixes "invalid params" error from certain chain RPCs.
---
 eth/mon2/monitor.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/eth/mon2/monitor.go b/eth/mon2/monitor.go
index ecc499f..45d52af 100644
--- a/eth/mon2/monitor.go
+++ b/eth/mon2/monitor.go
@@ -20,6 +20,10 @@ func (m *Monitor) MonAddr(cfg PerAddrCfg, cbfn EventCallback) {
 	// needed to provide evname to callback func
 	topicEvMap := EventIDMap(cfg.AbiStr)
 
+	if cfg.Topics == nil {
+		cfg.Topics = [][]common.Hash{}
+	}
+
 	q := &ethereum.FilterQuery{
 		Addresses: []common.Address{cfg.Addr},
 		Topics:    cfg.Topics,