Fix unused parameter warning in ctkLayoutViewFactory

Libs/Widgets/ctkLayoutViewFactory.h

@@ -180,6 +180,7 @@ public:
     this->setUseCachedViews(true);
   }
   virtual QWidget* createViewFromXML(QDomElement layoutElement){
+    Q_UNUSED(layoutElement);
     return new T;
     }
 };