Bug fix in StateRewardsSimple.

Wrong exception for out-of-bounds, so did not act "sparse" as intended.

prism/src/explicit/rewards/StateRewardsSimple.java

@@ -91,7 +91,7 @@ public class StateRewardsSimple extends StateRewards
 	{
 		try {
 			return stateRewards.get(s);
-		} catch (ArrayIndexOutOfBoundsException e) {
+		} catch (IndexOutOfBoundsException e) {
 			return 0.0;
 		}
 	}