Android Database null fragments

It keeps saying

     getReadableDatabse cant be invoked on null object which is the database. 

So my DataBase is null for some reason.

Main Activity: sent from fragment a to activity and activity updates fragment B

// Sends athlete information to athlete list
@Override
public void send(String confirmation) {
    if(confirmation == "Athlete Added!") {
        AthletesList athletesList = getAthleteListFragment();
        getSupportFragmentManager().beginTransaction().replace(R.id.frameLayout, athletesList, "athletesList");
        athletesList.addAthleteToList();
    }else{
        Toast.makeText(this, "Error: message confirmation incorrect!", Toast.LENGTH_SHORT).show();
    }
}
public AthletesList getAthleteListFragment(){
    AthletesList athletesList = (AthletesList) getSupportFragmentManager().findFragmentByTag("athletesList");
    if(athletesList == null){
        athletesList = new AthletesList();
    }
    return athletesList;
}

Create DataBase instance here in Activity created. This is a Fragment.

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    db = new dbHelper(getActivity());
}

Gets to the first log message but then says my DataBase is null.

public void addAthleteToList(){
    Log.e("", "Getting to addAthleteToList()");
    db.getReadableDatabase();
    Athlete athlete = db.getLastInsertedAthlete();
    db.close();
    Log.e("", "Athlete ID to be added: " + athlete.getAthleteID());