No collapsible button in Layout

The layout region panel has no collapsible button.

示例：

代码：

					
<div class="easyui-layout" style="width:700px;height:350px;">
	<div data-options="region:'north'" style="height:50px"></div>
	<div data-options="region:'south',split:true" style="height:50px;"></div>
	<div data-options="region:'east',split:true,title:'East',collapsible:false" style="width:250px;">
		<table id="tt" class="easyui-propertygrid" data-options="
				url: 'examples/layout/propertygrid_data1.json',
				method: 'get',
				showGroup: true,
				fit: true,
				border: false
			">
		</table>
	</div>
	<div data-options="region:'center',title:'Main Title',iconCls:'icon-ok',href:'examples/layout/_content.html'" style="padding:10px">
	</div>
</div>