fix: remove useless empty buff (#497)

* docs: LGTM badges

README.md

@@ -5,7 +5,8 @@
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+[![Total alerts](https://img.shields.io/lgtm/alerts/g/moscajs/aedes.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/moscajs/aedes/alerts/)
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lib/client.js

@@ -4,7 +4,6 @@ const mqtt = require('mqtt-packet')
 const EventEmitter = require('events')
 const util = require('util')
 const eos = require('end-of-stream')
-const empty = Buffer.allocUnsafe(0)
 const Packet = require('aedes-packet')
 const write = require('./write')
 const QoSPacket = require('./qos-packet')
@@ -73,8 +72,7 @@ function Client (broker, conn, req) {
     that._parsingBatch--
     if (that._parsingBatch <= 0) {
       that._parsingBatch = 0
-      var buf = empty
-      buf = client.conn.read(null)
+      var buf = client.conn.read(null)
       if (!client.connackSent && client.broker.decodeProtocol && client.broker.trustProxy && buf) {
         const { data } = client.broker.decodeProtocol(client, buf)
         if (data) {