Calling deleteAll:error: on an empty array causes a crash

[ghugues]

This will cause a crash :

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
    [PFObject deleteAll:@[] error:nil];
});

This is because deleteAllInBackground: returns a task whose result is not a boolean wrapped in an NSNumber when the array is empty.

[nlutsenko]

Indeed. Fixing in a bit.