fix: update manager not calling first frame methods once

Engine.Core/Systems/UpdateManager.cs

@@ -41,7 +41,10 @@ public class UpdateManager : UniverseObject
     private void OnPreUpdate(IUniverse sender, UniverseTime engineTime)
     {
         for (int i = toCallFirstFrameUpdates.Count - 1; i >= 0; i--)
+        {
             toCallFirstFrameUpdates[i].FirstActiveFrame();
+            toCallFirstFrameUpdates.RemoveAt(i);
+        }
 
         for (int i = preUpdateEntities.Behaviours.Count - 1; i >= 0; i--)
             preUpdateEntities.Behaviours[i].PreUpdate();