从bundle加载场景的资源后，切换场景a,在从场景a切换到场景b,然后从场景b切换回a 就会报错,
asset类型等都检查过了 都在调用cc.direct.runScene前查看过 场景无误,但是依然报错
错误如下
assets\scripts\Manager\SceneManager.ts:36 cc_SceneAsset {_name: “MainScene”, _objFlags: 0, _native: “”, scene: cc_Scene, asyncLoadAssets: null, …}
assets\scripts\Manager\SceneManager.ts:36 cc_SceneAsset {_name: “SpecialScene”, _objFlags: 0, _native: “”, scene: cc_Scene, asyncLoadAssets: null, …}
assets\scripts\Manager\SceneManager.ts:36 cc_SceneAsset {_name: “MainScene”, _objFlags: 0, _native: “”, scene: cc_Scene, asyncLoadAssets: null, …}
CCButton.js:304 Uncaught TypeError: Cannot read property ‘length’ of null
at cc_Scene.getChildByUuid (CCButton.js:304)
at 102.cc.Director.runSceneImmediate (cocos2d-js-for-preview.js:17611)
at 102.cc.Director. (cocos2d-js-for-preview.js:17645)
at 102.cc.Director.284.proto.emit (CCAudioClip.js:1)
at 102.cc.Director.mainLoop (shape-module.ts:371)
at callback (enum.ts:97)