Introduce ScalarValue.Null

src/Serilog/Capturing/DepthLimiter.cs

@@ -64,7 +64,7 @@ LogEventPropertyValue ILogEventPropertyValueFactory.CreatePropertyValue(object v
             if (depth == _maximumDestructuringDepth)
             {
                 SelfLog.WriteLine("Maximum destructuring depth reached.");
-                return new ScalarValue(null);
+                return ScalarValue.Null;
             }
 
             return null;

src/Serilog/Capturing/PropertyValueConverter.cs

@@ -120,7 +120,7 @@ LogEventPropertyValue CreatePropertyValue(object? value, bool destructureObjects
     LogEventPropertyValue CreatePropertyValue(object? value, Destructuring destructuring, int depth)
     {
         if (value == null)
-            return new ScalarValue(null);
+            return ScalarValue.Null;
 
         if (destructuring == Destructuring.Stringify)
         {

src/Serilog/Events/ScalarValue.cs

@@ -19,6 +19,11 @@ namespace Serilog.Events;
 /// </summary>
 public class ScalarValue : LogEventPropertyValue
 {
+    /// <summary>
+    /// Scalar value representing <see langword="null"/>.
+    /// </summary>
+    public static readonly ScalarValue Null = new(null);
+
     /// <summary>
     /// Construct a <see cref="ScalarValue"/> with the specified
     /// value.