lib.ptree.action_codec: support toplevel app classes and nil app args
lib.ptree.action_codec: support toplevel app classes and nil app args

snabbco/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,eugeneia/snabb,snabbco/snabb,eugeneia/snabb,snabbco/snabb,snabbco/snabb,snabbco/snabb