Listview from DB

I'm trying to get some data from a DB and display in a listview, but they logcat say Make sure the Cursor is initialized correctly before accessing data from it. This is my code

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cotizacionescolumna);
    lvCotizacion = (ListView)findViewById(R.id.lista_cotizaciones);
    list_cotizaciones = new ArrayList<String>();
    llenarLista();
    eventos();
}

public void llenarLista(){

        CotiCadSqlite db = new CotiCadSqlite(CotizacionesColumnnaActivity.this);
        Cursor c = db.obtenerNombresColumna();

        if(c.moveToFirst()){
            do{
                columna = c.getString(1);
                list_cotizaciones.add(columna);
            }while (c.moveToNext());
        }
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list_cotizaciones);
        lvCotizacion.setAdapter(adapter);
}