Revert recently added check to addFooterView

     */

    public void addFooterView(View v, Object data, boolean isSelectable) {

        if (mAdapter != null && ! (mAdapter instanceof HeaderViewListAdapter)) {

            throw new IllegalStateException(

                    "Cannot add footer view to list -- setAdapter has already been called.");

        }

        // NOTE: do not enforce the adapter being null here, since unlike in

        // addHeaderView, it was never enforced here, and so existing apps are

        // relying on being able to add a footer and then calling setAdapter to

        // force creation of the HeaderViewListAdapter wrapper

        FixedViewInfo info = new FixedViewInfo();

        info.view = v;