Bug in XmlDataManagerImpl::registerDiagnosticHandler()

[Markos Zaharioudakis]

I think that in this method, theContext is wrongly re-allocated. The problem is that the new context does not import the "fetch" and "xml" modules. I don't think it is necessary to re-allocate theContext. It is completely internal to the XmlDataManager, so it is ok if it uses the default diagnostic handler, because whatever errors it raises, they will be caught and handled by theDiganosticHandler of the XmlDataManager.