Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

Hi, I have been following a YouTube tutorial in enabling me to save a record to a csv file and I keep on getting the error Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) and Thread 1: Fatal error: Index out of range. I am not sure why this is the case, I would really appreciate the help!

Thanks

My code:

 @IBAction func btnCSV(_ sender: Any) {
 // File name
        let sFileName = "test.csv"

        

        let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String

        // Try change this to put url to onedrive

        let documentURL = URL(fileURLWithPath: documentDirectoryPath).appendingPathComponent(sFileName)

        let output = OutputStream.toMemory()

        

        let csvWriter = CHCSVWriter(outputStream: output, encoding: String.Encoding.utf8.rawValue, delimiter: ",".utf16.first!)

        // Header for CSV file watch at 6:47 on video to find how to get from data base to change this

        csvWriter?.writeField("Employee_ID")

        csvWriter?.writeField("Employee_Name")

        csvWriter?.writeField("Employee_Age")

        csvWriter?.writeField("Employee_Designation")

        csvWriter?.finishLine()

        

        // Array to add data for the employee

        var arrayofEmployeeData = [[String]]()

        

        arrayofEmployeeData.append(["123,Joe,18,developer"])

        arrayofEmployeeData.append(["223,John,29,engineer"])

        arrayofEmployeeData.append(["545,David,30,CEO"])

        // enumerated used for when there is mutliple data on one line

        for(elements) in arrayofEmployeeData.enumerated(){

            // Adds Employee ID

            csvWriter?.writeField(elements.element[0])

            // Adds Employee Name

            csvWriter?.writeField(elements.element[1])

            // Adds Employee Age

            csvWriter?.writeField(elements.element[2])

            // Adds Employee Designtion

            csvWriter?.writeField(elements.element[3])

            // Ends record and enables new record to be added

            csvWriter?.finishLine()

        }

        csvWriter?.closeStream()

        

        let buffer = (output.property(forKey: .dataWrittenToMemoryStreamKey)as? Data)!

        

        do{

            try buffer.write(to: documentURL)

        }

        catch{

            

        }

    }

}