Update arena.js

Author: ChrisAcrobat

arena.js

@@ -550,7 +550,7 @@ function tick(){
 		let participant = solidWorm.getParticipant();
 		participant.payload.response = null;
 		participant.postMessage(arenaClone).then(response => {
-			participant.payload.response = response.data;
+			participant.payload.response = response.message.data;
 			updateDirection(participant);
 		}).finally(()=>participant.payload.wormUpdated());
 		_participantPromises.push(new Promise(resolve => participant.payload.wormUpdated = resolve));