str_split_1 errors for empty character vector

[jl5000]

It would be useful if it just returned the original empty vector.

stringr::str_split_1(character(), " ")
#> Error in `stringr::str_split_1()`:
#> ! `string` must be a single string, not an empty character vector.

^{Created on 2023-03-16 by the reprex package (v2.0.1)}

[hadley]

I think the existing behaviour is correct because it requires a character vector of length 1.