labels = NULL in discrete_scale generates an error

[Henrik-P]

From ?discrete_scale:
"labels: NULL for no labels."

But:

df <- data.frame(x = 1, y = 1)

p <- ggplot(df, aes(x = x, y = y, color = factor(x))) + 
        geom_point()
p

p + scale_color_discrete(labels = NULL)
# Error in data.frame(values = scale_map(scale, breaks), labels = I(scale_labels(scale)),  : 
#                      arguments imply differing number of rows: 1, 0

See also this post on SO