[android help] asynctask not getting arraylist when called from a handler

I'm using a handler to start an asynctask but when doing so, my application crashes. The reason I am stuck is because if I start the asynctask via anything else (eg. onClickListener) then I can run it as many times, over and over again, and it works perfect every single time. As soon as I execute the asynctask from my handler, it immediately crashes the application with a NullPointerException.

My handler looks something like this

  public Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
        handler.post(new Runnable() {
          @Override
          public void run() {
            new sortNearby().execute();
          }

        });
    }
  };

Here is part of the stack trace from the application showing the exception

Caused by: java.lang.NullPointerException
at badams.android.app.fragments.MainMenu_NearbyFragment$sortNearby.doInBackground(MainMenu_NearbyFragment.java:100)

Line 100 of my code is the first line in the asynctask under doInBackground

protected String doInBackground(String... args) {
  for (int i = 0; i < global.places.size(); i++) { //this is line 100

I understand that the exception is more than likely coming from "global.places.size()" probably being null, but I am stuck on why its doing that only when called from the handler, as it works fine if I start the task from any other section of my code.

EDIT

As requested by @Raghunandan, here is the entire code block from doInBackground in my asynctask, which calculates the distance between a "place" and the user:

protected String doInBackground(String... args) {
  for (int i = 0; i < global.places.size(); i++) { //THIS IS LINE 100
    Location locationA = new Location("place");
    locationA.setLatitude(global.places.get(i).getLatitude());
    locationA.setLongitude(global.places.get(i).getLongitude());
    Location locationB = new Location("user");
    locationB.setLatitude(global.applicationLocationManager.getLatitude());
    locationB.setLongitude(global.applicationLocationManager.getLongitude());
    float dist = locationA.distanceTo(locationB);
    dist = dist / 1000;
    global.places.get(i).setDistance(dist);
    publishProgress(global.places.get(i));
  }
  return null;
}

.

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