[Rd] strsplit does not return correct value when spliting "" (PR#8777)

[charles.dupont at vanderbilt.edu]

Full_Name: Charles Dupont
Version: 2.2.0
OS: linux
Submission from: (NULL) (160.129.129.136)


when 

strsplit("", " ")

returns character(0)

where as 

strsplit("a", " ")

returns "a".

these return values are not constiant with each other.

Charles Dupont