Re-initialise tables with new game. Closes #2038

So, just when I thought I understood what went wrong... the bug comes back, this time with reproduction instructions. While #2025 was a legitimate bug fix, it's not for one that had actually manifested.

The problem here (#2038) is that the Lua environment isn't instanced per-game yet, so all module-local tables and variables really need to be re-initialised in onGameStart. Assuming that we hope to fix this situation in time, I've added an `XXX` comment.