Update SS_ExperienceHandler.txt

REALLY BAD BUG DETECTED.

If player 1 and player 2 both have shards equipped, when anyone kills a monster their shard scripts are called. Even if I were to limit it, there's no way to seperate multiple calls.

Each call to OnNPCKillEvent has an rid attached and the mob ID. I need to ensure it is called once, per player, per kill.