Crash upon trying to read a replay if random-player-pos is set to true

[Alayan-stk-2]

I'm getting this error when trying to read some replays:

[fatal ] Track: No start position for kart -1.

Either they are wrongly saved or there is a bug trying to read it, arguably both (STK should detect the error, not crash).

[Alayan-stk-2]

I traced it back to the "random-player-pos" setting. It is applied when trying to race replays, with predictably disastrous results.