StackOverflow when using OpenApiSchema Copy Constructor

src/Microsoft.OpenApi/Models/OpenApiSchema.cs

@@ -280,7 +280,7 @@ public OpenApiSchema(OpenApiSchema schema)
             MaxProperties = schema?.MaxProperties ?? MaxProperties;
             MinProperties = schema?.MinProperties ?? MinProperties;
             AdditionalPropertiesAllowed = schema?.AdditionalPropertiesAllowed ?? AdditionalPropertiesAllowed;
-            AdditionalProperties = new(schema?.AdditionalProperties);
+            AdditionalProperties = schema?.AdditionalProperties != null ? new(schema?.AdditionalProperties) : null;
             Discriminator = schema?.Discriminator != null ? new(schema?.Discriminator) : null;
             Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(schema?.Example);
             Enum = schema?.Enum != null ? new List<IOpenApiAny>(schema.Enum) : null;

test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs

@@ -463,5 +463,24 @@ public void SerializeAsV2ShouldSetFormatPropertyInParentSchemaIfPresentInChildre
             // Assert
             Assert.Equal(expectedV2Schema, v2Schema);
         }
+
+        [Fact]
+        public void OpenApiSchemaCopyConstructorSucceeds()
+        {
+            var baseSchema = new OpenApiSchema()
+            {
+                Type = "string",
+                Format = "date"
+            };
+
+            var actualSchema = new OpenApiSchema(baseSchema)
+            {
+                Nullable = true
+            };
+
+            Assert.Equal("string", actualSchema.Type);
+            Assert.Equal("date", actualSchema.Format);
+            Assert.True(actualSchema.Nullable);
+        }
     }
 }