[ISSUE #688] fix: type assert panic

diff --git a/consumer/pull_consumer.go b/consumer/pull_consumer.go
index 3a54194..0b0ef56 100644
--- a/consumer/pull_consumer.go
+++ b/consumer/pull_consumer.go
@@ -144,7 +144,7 @@
 	v, exist := queueCounterTable.Load(topic)
 	if !exist {
 		index = -1
-		queueCounterTable.Store(topic, 0)
+		queueCounterTable.Store(topic, int64(0))
 	} else {
 		index = v.(int64)
 	}