Fix event scripts' getEligibleParty

Cannot return a JavaScript array straight up
(otherwise you'll get a PolyglotMap):
it has to be converted first from inside the script.

scripts/event/BalrogBattle_Easy.js

@@ -103,7 +103,7 @@ function getEligibleParty(party) {      //selects, from the given party, the tea
         }
         
         if(!(hasLeader && eligible.length >= minPlayers && eligible.length <= maxPlayers)) eligible = [];
-        return eligible;
+        return Java.to(eligible, Java.type('net.server.world.MaplePartyCharacter[]'));
 }
 
 function setup(level, lobbyid) {