Always call `old_mem_ev`---exactly once.

I claim this is identical to the existing behaviour. Proof: consider the
boolean `room_id in sync_result_builder.joined_room_ids or has_join`.
If this is true, we make the first call to `_fetch_membership_event_at`.
Otherwise:

- `room_id not in sync_result_builder.joined_room_ids` and `not has_join`.
- The former means we continue on to inspect `events[-1].membership`.
- This is not `"join"`, or else `room_id in
  sync_result_builder.joined_room_ids` would be true.
- `has_join` is False, so we hit the `else` branch and make the second
  call to `_fetch_membership_event_at`.

So, assuming we continue beyond the first `continue`, we always call
fetch the old membership event exactly once. Do it up front to make the
reader's life easier.

0 files changed, 0 insertions, 0 deletions