Fixes #5430
Fixes #5533

We think that this small change avoids a race condition in the Options system where the garbage collector cleans up a weakref in this line:

max_id = max(store_ids)+1 if len(store_ids) > 0 else 0

It should not cause any other issues, because this would have been used when Python 2 was supported, at the time .keys() was returning a list. We may encounter this sort of issue in other places, if we don't handle weakrefs properly?