Lack of handling on _requires_ack if this.store throws error leads to infinite this._message_identifier increment

https://github.com/eclipse/paho.mqtt.javascript/blob/be026e0305f0ae5ed100015df25bbd20fac0a41b/src/paho-mqtt.js#L1201
should be
```javascript
if (this._message_identifier >= this.maxMessageIdentifier) {
```

because
```javascript
while(this._sentMessages[this._message_identifier] !== undefined) {
this._message_identifier++;
}
```
increments before this.store("Sent:", wireMessage); is called and this.store("Sent:", wireMessage); can throw an error, after which this._message_identifier remains incremented. Next time when this._requires_ack will be called it will be incremented again and this comparison will not work!

Start at src/paho-mqtt.js around line 1201 and trace _requires_ack, the _message_identifier loop, and the this.store("Sent:", wireMessage) call. Reproduce or inspect the error path where store throws, then verify that a subsequent _requires_ack call handles the incremented identifier without looping indefinitely.

Written by the indexing model from the issue text.