afaik you can fix it by changing this 2 lines of code inside the plugin:
change from:
item = @scene.pbUseItem($PokemonBag,pkmn) (line 210)
item = @scene.pbChooseItem($PokemonBag) (line 218)
into:
item = @scene.pbUseItem($bag,pkmn)
item = @scene.pbChooseItem($bag)