fix controller hot swapping

src/Input/Gamepad.cs

@@ -195,6 +195,20 @@ namespace MoonWorks.Input
 			};
 		}
 
+		public void Register(IntPtr handle)
+		{
+			Handle = handle;
+
+			IntPtr joystickHandle = SDL.SDL_GameControllerGetJoystick(Handle);
+			JoystickInstanceID = SDL.SDL_JoystickInstanceID(joystickHandle);
+		}
+
+		public void Unregister()
+		{
+			Handle = IntPtr.Zero;
+			JoystickInstanceID = -1;
+		}
+
 		internal void Update()
 		{
 			AnyPressed = false;

src/Input/Input.cs

@@ -95,7 +95,7 @@ namespace MoonWorks.Input
 					}
 					else
 					{
-						gamepads[slot].Handle = openResult;
+						gamepads[slot].Register(openResult);
 						System.Console.WriteLine($"Gamepad added to slot {slot}!");
 					}
 					return;
@@ -112,7 +112,7 @@ namespace MoonWorks.Input
 				if (joystickInstanceID == gamepads[slot].JoystickInstanceID)
 				{
 					SDL.SDL_GameControllerClose(gamepads[slot].Handle);
-					gamepads[slot].Handle = IntPtr.Zero;
+					gamepads[slot].Unregister();
 					System.Console.WriteLine($"Removing gamepad from slot {slot}!");
 					return;
 				}