GH Sender wrongly modifies the layers on defintion close

[didimitrie]

Step 0:

• I've read the contribution guidelines!

Expected Behaviour

Update should not be sent.

Actual Behaviour

The Gh sender, when you close the defintion, sends a final stream update call, modifying the layers field of the stream with wrong object counts.

Reproduction Steps & System Config (win, osx, web, etc.)

Create a sender, change the layer names, plug some data in. Close the grasshopper defintion and inspect the requests with fiddler.

[didimitrie]

closed in #209