Supplying aesthetics in scale_color_viridis does not work

[alanocallaghan]

Runs into #> Error in self$palette(n): attempt to apply non-function.

Reprex:

library("ggplot2")
library("viridis")
#> Loading required package: viridisLite

# works
ggplot(mtcars) +
    aes(wt, mpg, color = cyl) +
    geom_point() +
    scale_color_viridis()

# works
ggplot(mtcars) +
    aes(wt, mpg, color = cyl) +
    geom_point() +
    scale_color_viridis(aesthetics = "color")

# works
ggplot(mtcars) +
    aes(wt, mpg, color = factor(cyl)) +
    geom_point() +
    scale_color_viridis(discrete=TRUE)

# does not work
ggplot(mtcars) +
    aes(wt, mpg, color = factor(cyl)) +
    geom_point() +
    scale_color_viridis(discrete=TRUE, aesthetics = "color")
#> Error in self$palette(n): attempt to apply non-function

# works
ggplot(mtcars) +
    aes(wt, mpg, color = factor(cyl)) +
    geom_point() +
    scale_color_brewer()

# works
ggplot(mtcars) +
    aes(wt, mpg, color = factor(cyl)) +
    geom_point() +
    scale_color_brewer(aesthetics = "color")

[sjmgarnier]

Fixed with #89. Thanks for the PR.