[plt-scheme] plt-scheme Digest, Vol 8, Issue 1

Hello,

> (sxml:document
>   ...)
>
> This is the latest try
>
> string-prefix?: Non-string value (#<struct:pcdata>
> #<struct:element>)

This exception message turns out much confusing indeed. I'll add an
additional check to the `sxml:document' function to ensure that the argument
supplied has the string type.

Thank you for your feedback.
Dmitry