NSRangeException，不知道哪里出了问题

Question

我已经安装了MMLanScan pod，一切正常， 但是当我开始扫描局域网时，出现错误：

2019-01-29 14:33:50.166202+0100 JapoApps[439:42146] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndexedSubscript:]: index 0 beyond bounds for empty array'
*** First throw call stack:
(0x1f9c38ec4 0x1f8e09a50 0x1f9bb0494 0x1f9b33c68 0x10105a83c 0x10105b44c 0x10105afa0 0x1fa6ca790 0x101e2f824 0x101e30dc8 0x101e341c4 0x101e33604 0x101e421dc 0x101e42bc8 0x1f985517c 0x1f9857cec)
libc++abi.dylib: terminating with uncaught exception of type NSException

我不知道问题出在哪里以及如何调试它。

//协议功能

   func lanScanDidFindNewDevice(_ device: MMDevice!) {
        print(device.ipAddress)
    }

func lanScanDidFinishScanning(with status: MMLanScannerStatus) {
    print(status)
}

func lanScanDidFailedToScan() {
    print("FAIL")
}

//我的代码

var lanscanner : MMLANScanner!
override func viewDidLoad() {
    super.viewDidLoad()
    lanscanner = MMLANScanner(delegate: self)
    lanscanner.start()

}