Fix NullRef ex when loading the game

Author: Falki-git

MicroEngineerProject/MicroEngineer/MicroEngineerMod.cs

@@ -186,7 +186,7 @@ private void OnGUI()
             GUI.skin = MicroStyles.SpaceWarpUISkin;
 
             MicroUtility.RefreshGameManager();
-            if (MicroUtility.GameState.GameState == GameState.VehicleAssemblyBuilder)
+            if (MicroUtility.GameState?.GameState == GameState.VehicleAssemblyBuilder)
                 OnGUI_OAB();
             else
                 OnGUI_Flight();