webadmin: when loading page with webserver routes, internal services would always be shown with "admin" as internal services, and saving the handler would overwrite the correct setting

fix this by properly loading the correct internal service.

for issue #264 reported by kiekerjan, thanks!

webadmin/admin.ts

@@ -4847,7 +4847,7 @@ const webserver = async () => {
 							dom.option('Account', attr.value('account')),
 							dom.option('Webmail', attr.value('webmail')),
 							dom.option('Webapi', attr.value('webapi')),
-							attr.value(wi.Service),
+							prop({value: wi.Service}),
 						),
 					),
 				),