disconnect when connectoring a grid to one that has a projection

[InvalidArgument3]

23:01:43.2933 [ERROR]  Keen: System.NullReferenceException: Object reference not set to an instance of an object.
   at Sandbox.Game.Entities.Blocks.MyProjectorBase.previewGrid_OnBlockAdded(MySlimBlock obj)
   at System.Action`1.Invoke(T obj)
   at System.DelegateExtensions.InvokeIfNotNull[T1](Action`1 handler, T1 arg1)
   at Sandbox.Game.Entities.MyCubeGrid.NotifyBlockAdded_Patch1(MyCubeGrid this, MySlimBlock block)
   at Sandbox.Game.Entities.Cube.MyShipConnector.Weld(Nullable`1 masterToSlave)
   at Sandbox.Game.Entities.Cube.MyShipConnector.Weld()
   at Sandbox.Game.Entities.Cube.MyShipConnector.TryConnect()
   at VRage.Network.CallSite`7.Invoke(BitStream stream, Object obj, Boolean validate)
   at VRage.Network.MyReplicationLayer.Invoke(CallSite callSite, BitStream stream, Object obj, EndpointId source, MyClientStateBase clientState, Boolean validate)
   at Patched_VRage.Network.MyReplicationServerOnEvent_0(Object site, MyPacketDataBitStreamBase obj, CallSite sendAs, Object position, IMyNetObject source, Nullable`1 , EndpointId )
   at VRage.Network.MyReplicationLayer.OnEvent(MyPacketDataBitStreamBase data, NetworkId networkId, NetworkId blockedNetId, UInt32 eventId, EndpointId sender, Nullable`1 position)
   at VRage.Network.MyReplicationLayer.ProcessEvent(MyPacketDataBitStreamBase data, EndpointId sender)
   at VRage.Network.MyReplicationLayer.OnEvent(MyPacket packet)
   at Sandbox.Engine.Multiplayer.MyTransportLayer.ProcessMessage(MyPacket p)
   at Sandbox.Engine.Multiplayer.MyTransportLayer.HandleMessage(MyPacket p)
   at Sandbox.Engine.Networking.MyReceiveQueue.Process(NetworkMessageDelegate handler)
System.NullReferenceException: Object reference not set to an instance of an object.
   at Sandbox.Game.Entities.Blocks.MyProjectorBase.previewGrid_OnBlockAdded(MySlimBlock obj)
   at System.Action`1.Invoke(T obj)
   at System.DelegateExtensions.InvokeIfNotNull[T1](Action`1 handler, T1 arg1)
   at Sandbox.Game.Entities.MyCubeGrid.NotifyBlockAdded_Patch1(MyCubeGrid this, MySlimBlock block)
   at Sandbox.Game.Entities.Cube.MyShipConnector.Weld(Nullable`1 masterToSlave)
   at Sandbox.Game.Entities.Cube.MyShipConnector.Weld()
   at Sandbox.Game.Entities.Cube.MyShipConnector.TryConnect()
   at VRage.Network.CallSite`7.Invoke(BitStream stream, Object obj, Boolean validate)
   at VRage.Network.MyReplicationLayer.Invoke(CallSite callSite, BitStream stream, Object obj, EndpointId source, MyClientStateBase clientState, Boolean validate)
   at Patched_VRage.Network.MyReplicationServerOnEvent_0(Object site, MyPacketDataBitStreamBase obj, CallSite sendAs, Object position, IMyNetObject source, Nullable`1 , EndpointId )
   at VRage.Network.MyReplicationLayer.OnEvent(MyPacketDataBitStreamBase data, NetworkId networkId, NetworkId blockedNetId, UInt32 eventId, EndpointId sender, Nullable`1 position)
   at VRage.Network.MyReplicationLayer.ProcessEvent(MyPacketDataBitStreamBase data, EndpointId sender)
   at VRage.Network.MyReplicationLayer.OnEvent(MyPacket packet)
   at Sandbox.Engine.Multiplayer.MyTransportLayer.ProcessMessage(MyPacket p)
   at Sandbox.Engine.Multiplayer.MyTransportLayer.HandleMessage(MyPacket p)
   at Sandbox.Engine.Networking.MyReceiveQueue.Process(NetworkMessageDelegate handler)