bug


![2](https://user-images.githubusercontent.com/3305439/37333734-0ac9ce9e-26e5-11e8-81f5-97441faf2a7b.png)
![3](https://user-images.githubusercontent.com/3305439/37333756-17c438b4-26e5-11e8-988a-35034d27a82e.png)
![1](https://user-images.githubusercontent.com/3305439/37333774-205a95b8-26e5-11e8-9f17-71c81a2731d9.png)

一些比较旧的手机如 iPhone4s iPhone4c iPhone5会出现这种崩溃