Don't modify the layout of a container whilst its visible.

Fixes issue 4083

Change-Id: I6b939c7516b481366d0933f6b572d76616e89864
Reviewed-on: http://gerrit.dmdirc.com/1192
Reviewed-by: Gregory Holmes <greg@dmdirc.com>
Automatic-Compile: Gregory Holmes <greg@dmdirc.com>

src/com/dmdirc/addons/ui_swing/framemanager/buttonbar/ButtonBar.java

@@ -217,9 +217,10 @@ public final class ButtonBar implements FrameManager, ActionListener,
      * Removes all buttons from the bar and readds them.
      */
     private void relayout() {
-       buttonPanel.removeAll();
-       insertButtons(WindowManager.getRootWindows());
-       buttonPanel.repaint();
+        buttonPanel.setVisible(false);
+        buttonPanel.removeAll();
+        insertButtons(WindowManager.getRootWindows());
+        buttonPanel.setVisible(true);
     }
 
     /**