rewrite pic_get_args to check nparams first
rewrite pic_get_args to check nparams first

omasanori/picrin,dcurrie/picrin,picrin-scheme/picrin,ktakashi/picrin,koba-e964/picrin,koba-e964/picrin,leavesbnw/picrin,leavesbnw/picrin,ktakashi/picrin,leavesbnw/picrin,koba-e964/picrin,dcurrie/picrin,picrin-scheme/picrin,ktakashi/picrin,omasanori/picrin