update

Adding UnityEngine.Assertions.Assert to see if this passes standards and X-Ray.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs

@@ -1134,6 +1134,8 @@ public int MaximumFragmentedMessageSize
 
         internal void Initialize(bool server)
         {
+            UnityEngine.Assertions.Assert.IsNotNull(Singleton);
+
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             if (!DisableNotOptimizedSerializedType)
             {