encryptSecretStorageJSON issure

[Xiwen Xu]

 if let account =  Account.randomMnemonic() {
        debugPrint(account.mnemonicPhrase)
        debugPrint(account.address)
        account.encryptSecretStorageJSON("password") { (str) in
            debugPrint(str as Any)
        }
    }

will get nil Keystore string by Test use iPhone 5 , iOS 9;
but can get right value by use iPhone 5 , iOS 9 Simulator