string.byte with empty string

[Vaughan McAlley <ockegheim@...>]

Sorry if this has been discussed many times before, if it has, I
couldn't find it...

>print(type(string.byte("")))
=>stdin:1: bad argument #1 to 'type' (value expected)

Shouldn't string.byte return nil for an empty string?

Cheers,
Vaughan