当我们构建好资源打包安卓启动之后报空指针异常，有如下错误日志
at org.cocos2dx.lib.Cocos2dxAudioFocusManager.unregisterAudioFocusListener(Cocos2dxAudioFocusManager.java:121) at org.cocos2dx.lib.Cocos2dxActivity.onDestroy(Cocos2dxActivity.java:355)
可以参考https://github.com/cocos-creator/cocos2d-x-lite/pull/2060
