Your GRASS mapset region settings are at fault (even a temp dir needs to be set up). Try something like
region_check <- capture.output(execGRASS('g.region', flags = c('p'))
or cheat: open your mapset directly in GRASS and run g.region -p.
You will be able to set the region to match the file you imported by e.g. g.region raster=raster_image'