GLJPanel: No need to utilize AWT Component's default ImageObserver co…

…de - pixel data is ready when invoked.

src/jogl/classes/javax/media/opengl/awt/GLJPanel.java

@@ -1128,7 +1128,7 @@ public void doPaintComponent(Graphics g) {
         g.drawImage(offscreenImage, 0, 0,
                     offscreenImage.getWidth(),
                     offscreenImage.getHeight(),
-                    GLJPanel.this);
+                    null /* Null ImageObserver since image data is ready. */);
       }
     }