Fix build error on GoldMaster

Author: Lacyway

Fika.Core/FikaPlugin.cs

@@ -12,6 +12,7 @@
 using Fika.Core.Networking.Http;
 using Fika.Core.Networking.Websocket;
 using Fika.Core.Patching;
+using Fika.Core.UI;
 using Fika.Core.UI.Models;
 using Fika.Core.UI.Patches;
 using Fika.Core.Utils;