lua crashing on unrecognized strings

["Stuart P.Bentley" <stuart@...>]

Using the lua.exe interpreter provided with Lua for Windows, passing any 
letter to (os.date("%"..letter)) other than a-d, j, m, p, w-z, A, B, H, I, 
M, S, U, or W-Z is causing to crash (as in "has encountered a problem and 
needs to close" crash). This also happens when calling io.open with any 
undefined format string.

That can't be right, can it? (At the very least %C, %D, %e, %h, %n, %r, %R, 
%t, %T, %u, and %V should evaluate as they are defined in the standard 
(http://www.opengroup.org/onlinepubs/009695399/functions/strftime.html).)