Fixed unused parameter warning.

Author: robertosfield

include/osgQt/QWidgetImage

@@ -31,7 +31,7 @@ class OSGQT_EXPORT QWidgetImage : public osg::Image
         QGraphicsViewAdapter* getQGraphicsViewAdapter() { return _adapter; }
 
         virtual bool requiresUpdateCall() const { return true; }
-        virtual void update( osg::NodeVisitor* nv ) { render(); }
+        virtual void update( osg::NodeVisitor* /*nv*/ ) { render(); }
 
         void clearWriteBuffer();