address warnings when shading zero area

[simonpcouch]

Closes #528. With this PR:

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
library(forcats)
library(infer)

set.seed(123)

gss <- gss |> 
   mutate(class = fct_drop(class))

h0 <- gss |> 
   specify(class ~ college) |> 
   hypothesise("independence") |> 
   generate(1000, "permute") |> 
   calculate("chisq")

hA <- gss |> 
   specify(class ~ college) |> 
   calculate("chisq")

# two warnings
visualise(h0) +
 shade_p_value(hA, "right")

^{Created on 2024-03-25 with reprex v2.1.0}

[github-actions]

This pull request has been automatically locked. If you believe you have found a related problem, please file a new issue (with a reprex: https://reprex.tidyverse.org) and link to this issue.