tr visible colspan miss

<!DOCTYPE html>
<html>

<head>
	<title></title>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<script src="avalon.js" type="text/javascript"></script>
	<style type="text/css">
	.grid{
		border:1 solid #000;

	}
	</style>
</head>	
<body>
	<div ms-controller="grid" >
		<table cellpadding="0" border="1" cellspacing="0">
			<thead>
				<tr>
					<td>A</td>
					<td>B</td>
					<td>C</td>
				</tr>
			</thead>
			<tbody ms-each-item="data">
				<tr ms-visible="item.show">
					<td colspan="3">
						$index
					</td>
				</tr>
			</tbody>
		</table>
	</div>
	<script type="text/javascript">
	var $a = avalon;
	$a.ready(function(){
		
		var $vm = $a.define('grid',function(vm){
			vm.data = [
				{show:true},
				{show:false},
			]
		});
		setTimeout(function(){
			$vm.data[1].show = true;
		},2000);
		$a.scan();
	});

	</script>
</body>
</html>