Use delete to ensure removed bus markers are not kept

www/js/map.js

@@ -313,7 +313,7 @@
 								if (value.vehicle.oos || (value.vehicle.routeID != 24 && value.vehicle.routeID != 25)) {
 									if (markers['buses'][value.vehicle.id]) {
 										markers['buses'][value.vehicle.id].setMap(null);
-										markers['buses'][value.vehicle.id] = null;
+										delete markers['buses'][value.vehicle.id];
 									}
 
 									return;