fix redis nil in lua

Redis Nil bulk reply and Nil multi bulk reply -> Lua false boolean type

delayqueue.go

@@ -361,7 +361,7 @@ local unack2retry = function(msgs)
 	local retryCounts = redis.call('HMGet', KEYS[2], unpack(msgs)) -- get retry count
 	for i,v in ipairs(retryCounts) do
 		local k = msgs[i]
-		if v ~= nil and v ~= '' and tonumber(v) > 0 then
+		if v ~= false and v ~= nil and v ~= '' and tonumber(v) > 0 then
 			redis.call("HIncrBy", KEYS[2], k, -1) -- reduce retry count
 			redis.call("LPush", KEYS[3], k) -- add to retry
 		else