Some fixes for new gcc/clang

Minor fixes for newer gcc/clang. These issues were seen when using ubuntu-latest (Ubuntu 22.04) on Github Actions.

Fwk/AppFwk/cafViewer/cafOpenGLWidget.h

@@ -58,7 +58,7 @@ public:
                   const QGLFormat&         format,
                   QWidget*                 parent,
                   OpenGLWidget*            shareWidget = nullptr,
-                  Qt::WindowFlags          f           = nullptr );
+                  Qt::WindowFlags          f           = Qt::WindowFlags() );
     OpenGLWidget( OpenGLWidget* shareWidget, QWidget* parent, Qt::WindowFlags f = Qt::WindowFlags() );
 
     cvf::OpenGLContext* cvfOpenGLContext() const;