Cocos creator spine.setSkeletonData is error but why?

Cocos Creator
#1 
`const {ccclass, property} = cc._decorator;

@ccclass
export default class NewClass extends cc.Component {

@property(sp.SkeletonData)
data:sp.SkeletonData = null;

// LIFE-CYCLE CALLBACKS:

// onLoad () {}

start () {
    const spine = this.node.getComponent(sp.Skeleton);
    spine.setSkeletonData(this.data);
}

// update (dt) {}

}
`

spine.js:3264 Uncaught TypeError: Cannot read property ‘length’ of undefined
at new Skeleton (spine.js:3264)
at sp_Skeleton.setSkeletonData (Skeleton.js:483)
at NewClass.start (SpineTest.ts:25)
at CCClass.eval [as _invoke] (eval at createInvokeImpl (component-scheduler.js:256), :3:65)
at CCClass.invoke (component-scheduler.js:154)
at CCClass.startPhase (component-scheduler.js:447)
at 51.cc.Director.mainLoop (CCDirector.js:946)
at callback (CCGame.js:643)

what should i do?

#2

What version of Cocos Creator are you using? There was no problem in your test. I am using 2.2.0.

#3

@zzf_Cocos im using Cocos Creator v2.1.2

#4

What is your test platform? Web or native?