hadley/stringr — pull request #40 by seanchrismurphy (2014-10-24 14:14:47+00:00)
Title: Update str_pad to gracefully handle NA's (Address Issue #33)

Remove NA's from `lengths` to stop then getting in to str_dup, which can't handle them. Also reverts the character '`NA'`s to `NA` at the end.