Paho MQTT v1.2.1 occur crash on Android

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- [x] Bug exists Release Version 1.2.1 ( Master Branch)
- [?] Bug exists in MQTTv3 Client on Snapshot Version 1.2.1-SNAPSHOT (Develop Branch)
- [?] Bug exists in MQTTv5 Client on Snapshot Version 1.2.1-SNAPSHOT (Develop Branch)

If this is a bug regarding the Android Service, please raise the bug here instead: https://github.com/eclipse/paho.mqtt.android/issues/new

I've updated the Paho MQTT version from 1.2.0 to 1.2.1 in my Android project (with 1.1.1 of paho android service) to prevent the application crashes and bugs (to have bug-free version of the library) and it crashes with the following reason:

` Caused by: java.lang.ClassNotFoundException: Didn't find class "org.eclipse.paho.client.mqttv3.internal.TCPNetworkModuleFactory"`

Have someone faced the same problem?