[Rd] formatC with illegal input crashes Rgui (PR#7686)

[ehlers at math.ucalgary.ca]

Full_Name: Peter Ehlers
Version: rw2001pat (2005-02-03)
OS: Win XP
Submission from: (NULL) (136.159.61.115)


formatC(1, flag="s") crashes Rgui.
Similarly for flag=[SnZ].
Stupid input, of course, but I'm error-prone.

Peter