I’ll try to get a backtrace. The problem I have is that I haven’t seen the crash myself, I just get the odd report via Crashlytics.
The nil thing is to prevent Zombies with a deallocated parent object. As of about iOS8 if you don’t do that on e.g. a notification listener or delegate you can get a crash where the object looks for a dependant piece of memory that is now not there. This was my first attempt to fix the issue so is probably not doing much anyway.