Error at saving scematic

[Spieler1000]

command /saveschem :
trigger:
set {_region} to {regions::%arg-1%}
save {_region} as a schematic named arg-1:
copy entities: true
copy biomes: false
mask: mask from "stone,red_wool,blue_wool"
origin: location of player
remove entities: true
overwrite: true

Error: cannot invoke "me.cheezburga.skwe.api.utils.regions.RegionWrapper.world()" because "wrapper" is null