umbrello/umlwidgets/widgetbase.cpp

- Update copyright year.

umbrello/umlwidgets/widget_factory.cpp
- In function makeWidgetFromXMI loading of widgets which represent a
  UMLObject, if the UML object cannot be found then change the message
  from Debug to Error and return null pointer.
  Reason: Umbrello currently cannot handle forward references in the XMI
  of diagram objects.