cannot draw() a model with ordered factor as a random effect

[StefanoMezzini]

draw() returns the following error when asked to plot a model with an ordered factor as a random effect:
Error in .subset2(x, i, exact = exact) : attempt to select less than one element in integerOneIndex

I'm using gratia 0.5.1.9002, and I have updated all packages after updating R to 4.0.4.

The error occurs with both the github version and the CRAN version of gratia.

Reproducible example below:

library(mgcv)
library(gratia)
library(dplyr)
# re with ordered factors causes an error
gam(uptake ~ s(conc, Type, bs = 'fs', k = 5) + s(Plant, bs = 're'),
    family = Gamma('log'),
    data = CO2) %>%
  draw()

# re with unordered factor is ok
gam(uptake ~ s(Plant, bs = 're'),
    family = Gamma('log'),
    data = mutate(CO2, Plant = factor(Plant, ordered = FALSE))) %>%
  draw()

[gavinsimpson]

Thanks @StefanoMezzini — that was an easy fix in the end