NullPointerException in ReconnectTask and ConnectActionListener.onFailure, ClientComms.getNetworkModules() is null after close()

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- [X] Bug exists Release Version 1.2.5 ( Master Branch)
- [?] Bug exists in MQTTv3 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)
- [?] Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

Line with NPE is:
https://github.com/eclipse/paho.mqtt.java/blob/master/org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/internal/ConnectActionListener.java#L195

```
Exception in thread "MQTT Reconnect: Application" java.lang.NullPointerException: Cannot read the array length because the return value of "org.eclipse.paho.mqttv5.client.internal.ClientComms.getNetworkModules()" is null
at org.eclipse.paho.mqttv5.client.internal.ConnectActionListener.onFailure(ConnectActionListener.java:195)
at org.eclipse.paho.mqttv5.client.internal.ConnectActionListener.connect(ConnectActionListener.java:248)
at org.eclipse.paho.mqttv5.client.MqttAsyncClient.connect(MqttAsyncClient.java:783)
at org.eclipse.paho.mqttv5.client.MqttAsyncClient.attemptReconnect(MqttAsyncClient.java:1583)
at org.eclipse.paho.mqttv5.client.MqttAsyncClient.access$2(MqttAsyncClient.java:1578)
at org.eclipse.paho.mqttv5.client.MqttAsyncClient$ReconnectTask.run(MqttAsyncClient.java:1623)
at java.base/java.util.TimerThread.mainLoop(Timer.java:566)
at java.base/java.util.TimerThread.run(Timer.java:516)
```

Maybe `close()` should invoke `stopReconnectCycle()`?
Alternatively, `ReconnectTask` should not invoke `attemptReconnect()` if client was closed?

Start at ConnectActionListener.java:195 and trace the reconnect path through MqttAsyncClient.attemptReconnect(), ReconnectTask.run(), and ClientComms.getNetworkModules(). Reproduce the close-then-reconnect failure from the stack trace and verify that closing the client no longer causes a NullPointerException during reconnect handling.

Written by the indexing model from the issue text.