Bug: `geom_raster()` fails on devel

[teunbrand]

When x and y are discrete, one of the pixels seem to take over whole raster.

Reprex:

devtools::load_all("~/packages/ggplot2")
#> ℹ Loading ggplot2

df <- data.frame(
  x = rep(c("A", "B"), 2),
  y = rep(c("C", "D"), each = 2),
  z = letters[1:4]
)

ggplot(df, aes(x, y, fill = z)) +
  geom_raster()

^{Created on 2023-09-08 with reprex v2.0.2}