Merge pull request #73 in BA/design from ~XIAXIANG/design:dev to dev

* commit '267603ecee8de055e62dc833ddf57c63aab89469':
  rt

designer_base/src/com/fr/design/gui/icontainer/UIResizableContainer.java

@@ -100,6 +100,9 @@ public class UIResizableContainer extends JPanel {
     }
 
     public void setDownPane(JComponent downPane) {
+        if (this.downPane != null){
+            return;
+        }
         this.verticalToolPane = new VerticalToolPane();
         this.downPane = downPane;
         add(downPane);