Issue when deserializing XML with default namespace in ProvToolbox

[mf-16]

I found an issue in the newest version of ProvToolbox, 2.0.4, when handling the default namespace in XML.

Let me demonstrate the issue with this XML file:

<?xml version='1.0' encoding='ASCII'?>
<prov:document xmlns:ex="https://example.org/" xmlns="https://default.org/" xmlns:prov="http://www.w3.org/ns/prov#" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <prov:entity prov:id="e"/>
</prov:document>

When deserializing the identifier using the CustomQualifiedNameDeserializer#deserialize() method, it uses the DeserializerUtil#getAttributeValue() method.
On line 46 in DeserializerUtil#getAttributeValue() , when the identfier does not have a prefix, you used following:

xmlParser.getStaxReader().getNamespaceURI();

But this only gets the current element namespace which is prov, because it's in the <prov:entity> element.
Therefore, prov is registered as default namespace and the identfier of entity corresponds to IRI http://www.w3.org/ns/prov#/e.
However it should be https://default.org/e.
So, I think a better solution would be to use the following:

xmlParser.getStaxReader().getNamespaceURI("");

The statement above returns the default namespace. The correct namespace is registered as a default instead of the prov namespace being registered as default one.