AFNetworking/AFNetworking — pull request #251 by AquaGeek (2012-03-15 04:20:52+00:00)
Title: Check for null error pointer before setting it on the invocation

Some people like to run with scissors, but if you try to call

```objective-c
[invocation setArgument:error atIndex:4];
```

with a NULL error pointer, you get an exception. This only sets the error argument if it's non-NULL.