HierarchyPath parser now returns nil when
the path is empty (instead of a string slice with one
EmptyString element).
If the prefix is set to true, when calling the AsString
method on a nil HierarchyPath, only the separator will
be returned. This avoids a nil expr error coming from
the xmlquery library.
Use the Query and QueryAll functions from the xmlquery
package to be able to handle the errors ourselves and
avoid panics.
Added an integration tes for the special case where the
xml_root_path field is left empty. Before the change it
used to trim the root element from the path slice when
attempting to retrieve a the relative path slice.
