AndEngine GLES 2.0 – Power button issue – App Crashes onResume()-Collection of common programming errors

App crashes when i press power button to lock screen and press it again to unlock screen. App crashes after scren gets unlocked.

This is a stackTress i got in logcat:

05-09 18:46:57.254: E/AndroidRuntime(25354):    FATAL EXCEPTION: main
05-09 18:46:57.254: E/AndroidRuntime(25354):    java.lang.NullPointerException
05-09 18:46:57.254: E/AndroidRuntime(25354):    at org.andengine.ui.activity.BaseGameActivity.onResumeGame(BaseGameActivity.java:222)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at org.andengine.ui.activity.BaseGameActivity$4.run(BaseGameActivity.java:373)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at android.os.Handler.handleCallback(Handler.java:615)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at android.os.Handler.dispatchMessage(Handler.java:92)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at android.os.Looper.loop(Looper.java:137)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at android.app.ActivityThread.main(ActivityThread.java:4744)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at java.lang.reflect.Method.invokeNative(Native Method)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at java.lang.reflect.Method.invoke(Method.java:511)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-09 18:46:57.254: E/AndroidRuntime(25354):    at dalvik.system.NativeStart.main(Native Method)

Nullpointer Exception at onResumeGame() method of BaseGameActivityClass.

I have added this line in “activity” tag of manifest

 android:configChanges="orientation|keyboard|keyboardHidden"

in my GameActivity which extends BaseGameActivity i have added this

    @Override
    public void onPause() {
      super.onPause();
      mEngine.stop();
    }

    @Override
    protected void onResume() {
    // The activity has become visible (it is now "resumed").
       super.onResume();
       mEngine.start();
    }

What is wrong? What shall i do to stop crashing game on power button issue?