allow null authtokens to invalidateAuthToken

     * {@link android.Manifest.permission#MANAGE_ACCOUNTS} or

     * {@link android.Manifest.permission#USE_CREDENTIALS}

     *

     * @param accountType The account type of the auth token to invalidate

     * @param authToken The auth token to invalidate

     * @param accountType The account type of the auth token to invalidate, must not be null

     * @param authToken The auth token to invalidate, may be null

     */

    public void invalidateAuthToken(final String accountType, final String authToken) {

        if (accountType == null) throw new IllegalArgumentException("accountType is null");

        if (authToken == null) throw new IllegalArgumentException("authToken is null");

        try {

            if (authToken != null) {

                mService.invalidateAuthToken(accountType, authToken);

            }

        } catch (RemoteException e) {

            // won't ever happen

            throw new RuntimeException(e);