AFNetworking/AFNetworking — pull request #1703 by kaomte (2013-12-20 06:03:32+00:00)
Title: Don't run the task did complete callback if we don't have a delegate for...

... it.

If we don't have a delegate for it, it most likely means that the application terminated and this is a background download task that was "reattached" to the application when the session was recreated. This will cause a crash if we attempt to remove ourselves as an observer when we aren't observing it.