Unique in an ifelse statement in R

I am having trouble showing a vector of the unique values when I put call a unique on a vector in an ifelse statement as seen below.

> row <- c(1, 1, 1, 3, 3, 3)
> unique(row)
[1] 1 3
> ifelse(is.null(NULL), unique(row), 2)
[1] 1

I would like for the ifelse statement to return the same as unique(row) if indicated that it is NULL.

Thank you in advance!