small corrections on UsbHidTestApp

UsbHidTestApp/Program.cs

@@ -7,10 +7,10 @@ namespace UsbHidTestApp;
 
 internal class Program
 {
-    private static HidDevice _device;
+    private static HidDevice? _device;
     private static bool _continue;
-    private static Thread readThread;
-    private static List<HidDevice> lastDevices;
+    private static Thread? readThread;
+    private static List<HidDevice>? lastDevices;
     private static StringComparer stringComparer = StringComparer.OrdinalIgnoreCase;
 
 
@@ -89,6 +89,7 @@ internal class Program
 
                     _device.OpenDevice();
 
+
                     _device.Inserted += DeviceAttachedHandler;
                     _device.Removed += DeviceRemovedHandler;
 
@@ -151,7 +152,7 @@ internal class Program
     private static void DeviceAttachedHandler()
     {
         Console.WriteLine("Device attached.");
-        _device.ReadReport(OnReport);
+        _device?.ReadReport(OnReport);
     }
 
     private static void OnReport(HidReport report)
@@ -171,7 +172,7 @@ internal class Program
         {
             try
             {
-                var readData = _device.Read(100);
+                var readData = _device?.Read(100);
 
                 if (readData != null)
                 {