Fix null reference exception when calling GetLParam(...) on a zero …

…pointer (#276)

LightBulb.PlatformInterop/Internal/WndProcMessage.cs

@@ -1,13 +1,14 @@
-using System;
-using System.Runtime.InteropServices;
+using System.Runtime.InteropServices;
 
 namespace LightBulb.PlatformInterop.Internal;
 
 internal readonly record struct WndProcMessage(uint Id, nint WParam, nint LParam)
 {
-    public T GetLParam<T>() =>
-        (T?)Marshal.PtrToStructure(LParam, typeof(T))
-        ?? throw new InvalidOperationException(
-            $"Failed to deserialize WndProc message's lParam to {typeof(T)}."
-        );
+    public T? TryGetLParam<T>()
+        where T : struct =>
+        // If LParam is zero, marshaling will fail with null reference exception
+        // https://github.com/Tyrrrz/LightBulb/issues/275
+        LParam != 0
+            ? Marshal.PtrToStructure<T>(LParam)
+            : default(T?);
 }

LightBulb.PlatformInterop/PowerSettingNotification.cs

@@ -12,7 +12,7 @@ public partial class PowerSettingNotification(nint handle, Guid powerSettingId,
         m =>
         {
             // Filter out other power events
-            if (m.GetLParam<PowerBroadcastSetting>().PowerSettingId != powerSettingId)
+            if (m.TryGetLParam<PowerBroadcastSetting>()?.PowerSettingId != powerSettingId)
                 return;
 
             callback();