From d8095c40e55a6246c3cf34e70f6580d536defa42 Mon Sep 17 00:00:00 2001
From: Jared Wasinger <j-wasinger@hotmail.com>
Date: Tue, 14 Jan 2025 15:00:47 +0800
Subject: [PATCH] fix for when the code is run using the gasprice testBackend

---
 eth/gasprice/gasprice.go | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/eth/gasprice/gasprice.go b/eth/gasprice/gasprice.go
index ac91e9cab7..4fd3df7428 100644
--- a/eth/gasprice/gasprice.go
+++ b/eth/gasprice/gasprice.go
@@ -121,20 +121,22 @@ func NewOracle(backend OracleBackend, params Config, startPrice *big.Int) *Oracl
 	cache := lru.NewCache[cacheKey, processedFees](2048)
 	headEvent := make(chan core.ChainHeadEvent, 1)
 	sub := backend.SubscribeChainHeadEvent(headEvent)
-	go func() {
-		var lastHead common.Hash
-		for {
-			select {
-			case ev := <-headEvent:
-				if ev.Header.ParentHash != lastHead {
-					cache.Purge()
+	if sub != nil { // the gasprice testBackend doesn't support subscribing to head events
+		go func() {
+			var lastHead common.Hash
+			for {
+				select {
+				case ev := <-headEvent:
+					if ev.Header.ParentHash != lastHead {
+						cache.Purge()
+					}
+					lastHead = ev.Header.Hash()
+				case <-sub.Err():
+					return
 				}
-				lastHead = ev.Header.Hash()
-			case <-sub.Err():
-				return
 			}
-		}
-	}()
+		}()
+	}
 
 	return &Oracle{
 		backend:          backend,