SednaPy

Hello,

First, thanks for a much needed hook into Sedna!

While testing out SednaPy, I noticed the program would hang when sending
invalid XQuery's (ones with no result set).

I think I found where things are going wrong. The function fetchone(), in
the first condition, is trying to fetch the next row (self._getItem())
instead of returning nothing (None).

The only problem with this fix is you can't just throw the resultset into
etree because etree expects type Element. You must check the result before
continuing.

Thanks!