Tree组件lazy:true时isLeaf属性无效

指定load方法，load方法的部分内容如下：
```javascript
let children = [];
for(let file of files){
let {filename,...other} = file;
let fileLeaf = {filename:filename,children:[],path:path+'/'+filename,isLeaf:!file.attrs.dir,...other};
children.push(fileLeaf);
}
resolve(children);
```
指定的isLeaf属性无效，使用react-dev-tool审查Node节点时，Props下nodeModel属性无法展开，在Console面板显示错误信息
```
Uncaught TypeError: Cannot read property 'props' of undefinedgetPropertyFromData @ gateway.js:18942
get @ gateway.js:19302(anonymous function) @ backend.js:7516_
inspectResponse @ backend.js:7512
_handleMessage @ backend.js:7393
listener @ backend.js:86
```