as.polygons() fails on categorical SpatRaster with factors

[pat-s]

I've found the following categorical raster to fail when calling as.polygons() on it.
It works for a minimal example so something must be wrong/different with the custom raster in the following reprex?

remotes::install_github("mlr-org"/mlr3spatial")

library(mlr3spatial)
#> Loading required package: mlr3
library(terra)
#> terra version 1.4.11
#> 
#> Attaching package: 'terra'
#> The following object is masked from 'package:mlr3':
#> 
#>     resample

# works
stack_classif <- demo_stack_spatraster(0.1)
as.polygons(stack_classif)
#>  class       : SpatVector 
#>  geometry    : polygons 
#>  dimensions  : 9, 1  (geometries, attributes)
#>  extent      : 0, 1, 0, 1  (xmin, xmax, ymin, ymax)
#>  coord. ref. : lon/lat WGS 84 
#>  names       :   x_1
#>  type        : <num>
#>  values      :    -3
#>                   -2
#>                   -1

# also works
r1 <- rast(matrix(rep(c("FALSE", "TRUE"), 3), nrow = 2))
value <- data.frame(ID = c(0, 1), y = c("negative", "positive"))
setCats(r1, layer = "y", value = value)
as.polygons(r1)
#>  class       : SpatVector 
#>  geometry    : polygons 
#>  dimensions  : 2, 1  (geometries, attributes)
#>  extent      : 0, 1, 0, 1  (xmin, xmax, ymin, ymax)
#>  coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#>  names       :    lyr.1
#>  type        :    <chr>
#>  values      : negative
#>                positive

# fails
value <- data.frame(ID = c(0, 1), y = c("negative", "positive"))
setCats(stack_classif, layer = "y", value = value)

as.polygons(stack_classif)
#> Error in .local(x, i, j = j, ..., value): i > 0 && i <= ncol(x) is not TRUE

^{Created on 2021-10-21 by the reprex package (v2.0.1)}

[rhijmans]

Thanks, I believe this has now been fixed. The error was related to having multiple layers in the SpatRaster, and a categorical layer that is not the first layer. Note that as.polygons will only process the first layer of dissolve=TRUE