CheckBox inside of RecyclerView

I am having CheckBox inside of RecyclerView. I am setting item by storing values into Object class List<CartRes>where the data have been gotten from DataBase and I populated these into RecyclerView. But when I click CheckBox app is closed due to NullPointer Exception.

MyCode:

ChatListAdapter.java:

    holder.chkSelected.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            CheckBox cb = (CheckBox) v;
            CartRes cartRes = (CartRes) cb.getTag(); // Getting NPE at here.

            cartRes.setSelected(cb.isChecked());
            RestaurantFilter.get(pos).setSelected(cb.isChecked());

            Toast.makeText(
                    v.getContext(),
                    "Clicked on Checkbox: " + cb.getText() + " is "
                            + cb.isChecked(), Toast.LENGTH_LONG).show();
        }
    });