forced close when notification goes to activity

I'm making a project in Android.

When I'm in activity (groups.class) I'm calling to this function (declared inside the activity):

  public void lookForGroups()
    {
        int seconds = 20;

           Intent myIntent = new Intent(Groups.this, GroupsTaskAlarmChecker.class);
           pendingIntent = PendingIntent.getService(Groups.this, 0, myIntent, 0);

           AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);

           Calendar calendar = Calendar.getInstance();
           calendar.setTimeInMillis(System.currentTimeMillis());
           calendar.add(Calendar.SECOND, 10);
           alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), seconds * 1000, pendingIntent);

    }

inside the Service I connect to php in web and receive an answer and then I create a Notification (declarated inside the Service) sending a message to a handler that call to function notifyNew().

public class GroupsTaskAlarmChecker extends Service implements Runnable {
         public void run() { php call and send msg to handler to call notify function}
         private void notifyNew() { 
        Intent intentNot = new Intent(this, Groups.class);

        Notification notification = new Notification(R.drawable.icon, "changes", System.currentTimeMillis());
        notification.setLatestEventInfo(this, getString(R.string.app_name), getString(R.string.notifiedGroup), 
                PendingIntent.getActivity(this, 0, intentNot, PendingIntent.FLAG_CANCEL_CURRENT));

        notification.defaults |= Notification.DEFAULT_SOUND;
        notification.defaults |= Notification.DEFAULT_VIBRATE;

        notification.defaults |= Notification.DEFAULT_LIGHTS;
        notification.flags = Notification.FLAG_AUTO_CANCEL;

        try
        {
            notification.ledARGB = 0xff00ff00;
            notification.ledOnMS = 300;
            notification.ledOffMS = 1000;
            notification.flags |= Notification.FLAG_SHOW_LIGHTS;
        }catch(Exception ex)
        {           
        }           
        manager.notify(APP_ID_NOTIFICATION, notification);
}  
}

I want to go again to activity "Groups" again when the notification is touched. All of that works fine but when I touch the notification logCat shows that...

03-01 17:52:50.663: E/AndroidRuntime(17019): FATAL EXCEPTION: main
03-01 17:52:50.663: E/AndroidRuntime(17019): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.org.tfc_android/com.org.tfc_android.Groups}: java.lang.NullPointerException
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2304)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2354)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread.access$600(ActivityThread.java:150)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.os.Looper.loop(Looper.java:137)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread.main(ActivityThread.java:5193)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at java.lang.reflect.Method.invokeNative(Native Method)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at java.lang.reflect.Method.invoke(Method.java:511)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at dalvik.system.NativeStart.main(Native Method)
03-01 17:52:50.663: E/AndroidRuntime(17019): Caused by: java.lang.NullPointerException
03-01 17:52:50.663: E/AndroidRuntime(17019):    at com.org.tfc_android.Groups.onCreate(Groups.java:61)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.Activity.performCreate(Activity.java:5104)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
03-01 17:52:50.663: E/AndroidRuntime(17019):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2258)
03-01 17:52:50.663: E/AndroidRuntime(17019):    ... 11 more

There are a Forced close but later goes right to Activity Groups Somebody could help me with that?

SOLVED: solved add intentNot.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP); when create Intent before Notification.

I solved add intentNot.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP); thanks to @FahadIshaque