[BUG] Levels not marked as completed if multiple lemmings exit at once

[namida]

If multiple lemmings exit on the same frame, and this causes the saved amount to jump from a value below the requirement to one above it (without ever hitting the requirement exactly), the level does not get marked as completed. (A previous theory about the cause of this turned out to be incorrect.)

[namida]

Found the cause of this to be completely different to what I previously thought; it just so happened the level where this was occurring had both factors and the other one seemed more likely to be the reason.

Regardless, fixed in commit 0db5817.