Fix a bug of failing to get keys from MapEx in some old browsers
Fix a bug of failing to get keys from MapEx in some old browsers

partridgejiang/Kekule.js,partridgejiang/Kekule.js,partridgejiang/Kekule.js,partridgejiang/Kekule.js,partridgejiang/Kekule.js,partridgejiang/Kekule.js