Don't add the modifier for service name if it is not configured (#10832…

…) (#11024)

Check if service.name is configured, and if not, don't add the modifier
so no additional overhead is added for all events.

(cherry picked from commit 775568d)

metricbeat/mb/module/options.go

@@ -64,14 +64,17 @@ func WithMetricSetInfo() Option {
 // given to the `service.name` setting in the module configuration.
 func WithServiceName() Option {
 	return func(w *Wrapper) {
+		if w.Module == nil {
+			return
+		}
+		serviceName := w.Module.Config().ServiceName
+		if serviceName == "" {
+			return
+		}
 		modifier := func(_, _ string, event *mb.Event) {
 			if event == nil {
 				return
 			}
-			serviceName := w.Module.Config().ServiceName
-			if serviceName == "" {
-				return
-			}
 			if event.RootFields == nil {
 				event.RootFields = common.MapStr{}
 			} else if current, err := event.RootFields.GetValue("service.name"); err == nil && current != "" {