fix: strategyFn index out of range if proxies changed (#2330)

adapter/outboundgroup/loadbalance.go

@@ -194,7 +194,7 @@ func strategyStickySessions(url string) strategyFn {
 		key := utils.MapHash(getKeyWithSrcAndDst(metadata))
 		length := len(proxies)
 		idx, has := lruCache.Get(key)
-		if !has {
+		if !has || idx >= length {
 			idx = int(jumpHash(key+uint64(time.Now().UnixNano()), int32(length)))
 		}