Better error message if outcome has 0 columns

[EmilHvitfeldt]

Extracted from: https://stackoverflow.com/questions/77305226/why-am-i-receiving-the-error-object-not-found

If someone uses step_dummy() or some other ways in {recipes} to remove the outcome, then parsnip:::check_outcome() throws a wonderfully bad error 😄

library(tidymodels)

rec <- recipe(Species ~ ., data = iris) %>%
  step_dummy(Species)

svm_spec <- 
  svm_rbf() %>% 
  set_engine("kernlab") %>% 
  set_mode("classification")

wflow <- workflow() %>% 
  add_model(svm_spec) %>% 
  add_recipe(rec)

fit(wflow, iris)
#> Error: object '.' not found

^{Created on 2023-10-16 with reprex v2.0.2}

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