Fixed #5833: add a check to cc.Scale9Sprite._cacheScale9Sprite
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into Iss5833_Scale9Sprite
Merge pull request #2147 from dingpinglv/Iss5833_Scale9Sprite

Fixed #5833: add a check to cc.Scale9Sprite._cacheScale9Sprite