Invalid Packet Type

After some time of usage, the Pharo-client just disconnects with the error:

relates to REASON_CODE_INVALID_MESSAGE

```
Paket nicht erkannt (32108)
at org.eclipse.paho.client.mqttv3.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:31)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:99)
at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:137)
```

Restarting the application immediately produces the same error again, only restarting the broker helps (for some time)

So, apparently the broker is sending "something" invalid there.

However, this exception can't be handled code-wise (from the app) because paho itself decides that this is a non-recoverable error and goes into stop-state. at:

```
catch (MqttException ex) {
//@TRACE 856=Stopping, MQttException
log.fine(CLASS_NAME,methodName,"856",null,ex);
synchronized (lifecycle) {
target_state = State.STOPPED;
}
// Token maybe null but that is handled in shutdown
clientComms.shutdownConnection(token, ex);
}
```

Any Workarounds to "reject / ignore" invalid messages?
Other MQTT-Clients are just working fine at the same time.

Start with MqttInputStream.readMqttWireMessage and the ExceptionHelper.createMqttException stack trace, then follow CommsReceiver.run into clientComms.shutdownConnection. Reproduce the invalid-packet disconnect if possible and determine whether the client can reject or ignore the message without entering STOPPED state; done means the behavior is covered by a regression test.

Written by the indexing model from the issue text.