The path expression namespace::xml should always
return a node-set containing a single node (provided
the context node is an element).
With the tinytree model, it returns an empty node-set.
Test case added, nspc35.
The problem is present in 6.5.1, in 7.0, and probably
in earlier releases back to 6.0.
Found by MHK while testing changes for 7.1.