How to handle System.ArgumentNullException?

Question

When I am debugging the below code block, I am getting System.ArgumentNullException .

public string StartDeviceDiagnosis(DiagnosticsOption diagnosticsOption)
        {
            var aggregator = ServiceProviderHandle.ServiceProvider.GetService<**IAggregator**>();
            this.CreateDeviceStatusReport(DiagnosticConstant.DeviceStatusReportHTMLFileName);
            return aggregator.AggregateLogs(diagnosticsOption, true);
        }

System.ArgumentNullException: 'Value cannot be null. Parameter name: provider'

I tried adding try-catch block to handle the exception, but I wasn't able to do that as the method has to return a string.