解决使用SDWebImage加载图片，图片为空的问题

<Error>: CGContextDrawImage: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jun  4 11:37:12  aiJiaApp[2059] <Error>: CGBitmapContextCreateImage: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

报这样的错误,解决方法：

在SDWebImageDecoder.m文件里加入

if (image == nil) {

        return image;
    }