Avoid sending additionalData tag if there isn't any

Change-Id: Ie0d55ece8f0a46e987845d974aab997baf32df21
diff --git a/src/server/dial_server.c b/src/server/dial_server.c
index 9efff06..43413b4 100644
--- a/src/server/dial_server.c
+++ b/src/server/dial_server.c
@@ -230,18 +230,22 @@
             "  <name>%s</name>\r\n"
             "  <options allowStop=\"%s\"/>\r\n"
             "  <state>%s</state>\r\n"
-            "%s"
-            "  <additionalData>\n"
-            "%s"
-            "\n  </additionalData>\n",
+            "%s",
             origin_header,
             DIAL_VERSION,
             app->name,
             canStop ? "true" : "false",
             app->state ? "running" : "stopped",
             app->state == kDIALStatusStopped ?
-                    "" : "  <link rel=\"run\" href=\"run\"/>\r\n",
+                    "" : "  <link rel=\"run\" href=\"run\"/>\r\n");
+    if (strlen(dial_data)>0) {
+        mg_printf(
+            conn,
+            "  <additionalData>\r\n"
+            "%s"
+            "\r\n  </additionalData>\r\n",
             dial_data);
+    }
     if (app->callbacks.service_data_cb != NULL) {
         struct CastServiceData serviceData = app->callbacks.service_data_cb(ds, app_name, app->run_id, app->callback_data);
         mg_printf(conn,