添加声音文件时报错

[robinma]

添加声音mp3文件，当编译时报错，执行代码如下：
`
....
const voicePath = setPath(pathId, "voice.mp3");
...
const vioce_s2 = new FFAudio({ src: voicePath });
scene2.addChild(vioce_s2);

....
scene2.setDuration(5);
creator.addChild(scene2);

`
返回错误信息如下：

(node:4663) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'remove' of undefined
at Layer.appendChild (/Users/mzj/mw/git/video-demo/node_modules/spritejs/dist/spritejs.js:34380:10)
at FFScene.addChild (/Users/mzj/mw/git/video-demo/node_modules/ffcreator/lib/node/cons.js:55:18)
at createFFTask (/Users/mzj/mw/git/video-demo/src/videoEnglish.js:128:10)
at processTicksAndRejections (internal/process/task_queues.js:82:5)
(node:4663) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:4663) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

以上如果删除添加FFAudio代码，执行是成功的，加上则报错，看能否解决。

[drawcall]

To add audio, please use the addAudio method