It turns out that this change revealed unit tests written incorrectly
(and untested), or maybe which became broken (not testing) because of
some previous assertXPath change? They incorrectly used 3-arg form of
it to check node content equality to passed string, while in fact, an
attribute was looked for with that name, and its empty return tested
to match default empty 4th argument.

Change-Id: If24e18518543102d115a22a6282e4cca9cf694e2
Reviewed-on: https://gerrit.libreoffice.org/70581Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Mike Kaganski <mike.kaganski@collabora.com>