Ensure skin `InstantiationInfo` is updated when saving

osu.Game/Skinning/SkinImporter.cs

@@ -232,6 +232,9 @@ public void Save(Skin skin)
         {
             skin.SkinInfo.PerformWrite(s =>
             {
+                // Update for safety
+                s.InstantiationInfo = skin.GetType().GetInvariantInstantiationInfo();
+
                 // Serialise out the SkinInfo itself.
                 string skinInfoJson = JsonConvert.SerializeObject(s, new JsonSerializerSettings { Formatting = Formatting.Indented });