Fixed set_theme() default value for new

Author: VisruthSK

R/theme-current.R

@@ -93,7 +93,7 @@ theme_get <- get_theme
 #' @rdname get_theme
 #' @param new new theme (a list of theme elements). Sets theme to the default ([theme_grey()]) if `new` isn't supplied.
 #' @export
-set_theme <- function(new) {
+set_theme <- function(new = null) {
   new <- new %||% ggplot_global$theme_default
   check_object(new, is_theme, "a {.cls theme} object")
   old <- ggplot_global$theme_current