Fail to invalidate cmp inside borderlayout if flex=true...

The bug can only be caused by the fact that debugJS is true.

<zk>
<borderlayout height="100px">
<center flex="true">
<div id="div">Please turn on the debug JS configuration because it can only be appeared in that case.
<button label="Click Me" onClick="div.invalidate();"/>
</div>
</center>
</borderlayout>
</zk>