Proper handling of TypeName = null from appsettings.json (#420)

Co-authored-by: Marius Wingerei <[email protected]>

Author: mariwing

src/Serilog.Sinks.Elasticsearch/LoggerConfigurationElasticSearchExtensions.cs

@@ -204,10 +204,7 @@ public static LoggerConfiguration Elasticsearch(
                 options.TemplateName = templateName;
             }
 
-            if (!string.IsNullOrWhiteSpace(typeName))
-            {
-                options.TypeName = typeName;
-            }
+            options.TypeName = !string.IsNullOrWhiteSpace(typeName) ? typeName : null;
 
             options.BatchPostingLimit = batchPostingLimit;
             options.BatchAction = batchAction;