XmlComment example tags for string properties where the example is <e…

…xample>null</example> will now resolve to a null value instead of the string "null"

src/Swashbuckle.AspNetCore.SwaggerGen/XmlComments/XmlCommentsSchemaFilter.cs

@@ -48,7 +48,7 @@ private void ApplyMemberTags(OpenApiSchema schema, SchemaFilterContext context)
             var exampleNode = fieldOrPropertyNode.SelectSingleNode("example");
             if (exampleNode != null)
             {
-                var exampleAsJson = (schema.ResolveType(context.SchemaRepository) == "string")
+                var exampleAsJson = (schema.ResolveType(context.SchemaRepository) == "string") && !exampleNode.Value.Equals("null")
                     ? $"\"{exampleNode.InnerXml}\""
                     : exampleNode.InnerXml;