AFNetworking/AFIncrementalStore — pull request #72 by pitiphong-p (2012-10-13 11:35:24+00:00)
Title: Ignore the null (nil) value in the fetched relationship and relationship is optional

The service I use sometime return the nil in the returned JSON. So I configure the Managed Object Model that relationship to optional.
BTW AFIS will crash in
```
- (void)insertOrUpdateObjectsFromRepresentations:
ofEntity:
fromResponse:
withContext:
error:
completionBlock:
```
methods with unrecognized selector exception on line
```
NSMutableArray *mutableManagedObjects = [NSMutableArray arrayWithCapacity:[representationOrArrayOfRepresentations count]];
```
because the representationOrArrayOfRepresentations is [NSNull null]