java.lang.NullPointerException appears a lot

[wpcfan]

We are seeing many occurrences of the following exception, any idea what might lead to this?

java.lang.NullPointerException
    at com.soulkey.mqtt.MQTTManager.sendMsgOnMqttThread(MQTTManager.java:387)
    at com.soulkey.mqtt.MQTTManager.sendMsgOnMqttThread(MQTTManager.java:397)
    at com.soulkey.callcall.socketInterface.SocketInterfaces.messge(SocketInterfaces.java:123)
    at com.soulkey.callcall.activity.AskActivity.publishMsg(AskActivity.java:505)
    at com.soulkey.callcall.activity.AskActivity.sendMessage(AskActivity.java:470)
    at com.soulkey.callcall.activity.AskActivity.access$200(AskActivity.java:78)
    at com.soulkey.callcall.activity.AskActivity$3.onOptionSelected(AskActivity.java:260)
    at com.soulkey.plugins.inputLayout.InputLayout$5.onClick(InputLayout.java:315)
    at android.view.View.performClick(View.java:4444)
    at android.view.View$PerformClick.run(View.java:18445)
    at android.os.Handler.handleCallback(Handler.java:733)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:136)
    at android.app.ActivityThread.main(ActivityThread.java:5133)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
    at dalvik.system.NativeStart.main(Native Method)