The referenced page reports an exception at line 83, when it actually happens at line 69
Created attachment 29639 [details]
Here's a reduction that's off by one line.
This off-by-one error occurs because the inspector doesn't include the first line of the document:
<?xml version="1.0" encoding="utf-8" standalone="no"?>
I think Oliver's original example is more complicated than this.
Works for me in ToT, please reopen if you can still reproduce a problem.