"of null" means that one of the objects you're using or referencing does not exist.
either the call is in the wrong place (has no event to be targeted), or the animation 385 does not exist (by default MV has only 120 animmation, have you really added almost 300 more animations?) or so on.
for more help than that we need to learn the context of that script call, where you are using it (screenshot of the event or specify the plugin code) and so on.