[bug] Crash when sending retained message with QoS = 2

[jbaramidze]

System Information

• Aedes: 0.44.0
• NodeJS: 14.15.4
• OS: macOS 10.15.7 / Darwin 19.6.0
• Arch: x86_64

Describe the bug
aedes-persistence-redis crashes when trying to send retained message of QoS=2

To Reproduce

• Launch Aedes broker with aedes-persistence-redis persistence layer. I have used mqtt-cli package for it, with the following config:

module.exports = {
  protos: ['tcp', 'ws'],
  host: '127.0.0.1',
  wsPort: 6423,
  brokerId: 'aedes-cli',
  persistence: {
    name: 'redis',
    options: {
	    url: 'redis://127.0.0.1'
    }
  },
  key: null,
  cert: null,
  rejectUnauthorized: true,
  verbose: false,
  veryVerbose: false,
  noPretty: false
}

• Connect with a client C1 (non-clean session), and send message to any topic with {retain: true, qos: 2}
• Disconnect C1
• Connect with a client C2 (non-clean session), and subscribe to a topic used above with {qos: 2}
• Aedes crashes inside aedes-persistence-redis with error ERROR: unknown key

Expected behavior
Should not crash

Additional context
After debugging a little, it seems that it crashes when it's trying to send PubRel packet of the retained message. Aedes invokes RedisPersistence.prototype.outgoingUpdate, which calls augmentWithBrokerData. Inside this function, var key = that.messageIdCache.get(messageIdKey) returns undefined, which causes the crash

[jbaramidze]

To help with reproducing, client codes:
C1:

import mqtt from "mqtt";
const LOCAL_URL = "ws://localhost:6423/mqtt";
var client = mqtt.connect(LOCAL_URL, {clientId: `3:someString`, username: "3", clean: false})
client.on('connect', function (pack) {
    client.publish(`broadcast/5`, `HELLO ${process.argv[2]}`, {retain: true, qos: 2});
});

C2:

import mqtt from "mqtt";
const LOCAL_URL = "ws://localhost:6423/mqtt";
var client = mqtt.connect(LOCAL_URL, {clientId: `2:someString`, username: "2", clean: false})
client.on('connect', function (pack) {
    client.subscribe(`broadcast/5`, {qos: 2}, function (err, s) {
        console.log("Error on subscribe: ", err);
    });
});

[robertsLando]

@jbaramidze Are you able to submit a PR to fix the issue? It seems you have found the line causing the bug