My client crashed on a DS when I selected a blueprint from the F10 menu. This blueprint, however, contained blocks from mods that were not loaded in this world. I am unsure if the following crash log has something to do with that, but if so, I suggest to add a check for missing mods and ask the user if he wants to cancel or to proceed and remove the missing blocks from the blueprint.

Exception occurred: VRage.MyUpdateSchedulerException: Failed to execute Void RunSingleFrame() on Medieval.MyMedievalGame
 ---> VRage.MyUpdateSchedulerException: Failed to execute Void Update() on Medieval.GameSystems.Building.MyGridPlacer
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at VRage.Game.Components.MyPositionComponent.SetWorldMatrix(MatrixD worldMatrix, Object source, Boolean forceUpdate)
   at Medieval.GameSystems.Building.MySceneBuildingState.SetTransform(MatrixD newTransform)
   at Medieval.GameSystems.Building.MyGridPlacer.Update()
   at VRage.Components.MyUpdateScheduler.RunFixedUpdates()
   --- End of inner exception stack trace ---
   at VRage.Components.MyUpdateScheduler.ReportError(Delegate action, Exception error)
   at VRage.Components.MyUpdateScheduler.RunFixedUpdates()
   at VRage.Components.MyUpdateScheduler.RunUpdates(TimeSpan currentTime)
   at Sandbox.Game.World.MySession.UpdateComponents()
   at Sandbox.Game.World.MySession.Update(MyTimeSpan updateTime)
   at Sandbox.MySandboxGame.Update()
   at Sandbox.Engine.Platform.Game.UpdateInternal()
   at Sandbox.Engine.Platform.Game.RunSingleFrame()
   at VRage.Components.MyUpdateScheduler.RunFixedUpdates()
   --- End of inner exception stack trace ---
   at VRage.Components.MyUpdateScheduler.ReportError(Delegate action, Exception error)
   at VRage.Components.MyUpdateScheduler.RunFixedUpdates()
   at VRage.Components.MyUpdateScheduler.RunUpdates(TimeSpan currentTime)
   at Sandbox.Engine.Platform.MySandboxUpdate.<RunLoop>b__18_0()
   at VRage.Utils.FixedLoop.Run(Action tickCallback)
   at Sandbox.Engine.Platform.MySandboxUpdate.RunLoop()
   at Medieval.MyProgram.Main(String[] args)
=============================== FATAL EXCEPTION ================================```