Fix(rhino): missing render material of layers on second send

[oguzhankoral]

When creating a layer on receive we cannot set RenderMaterial to layer. (RhinoCommon API limitation, it tested)
We can only set render material index of layer on receive. So for the second send, we also need to check its index!

BEFORE (see 2 render material proxies on scene explorer)

AFTER (see 6 render material proxies on scene explorer)

[linear]

CNX-468 Rhino: Layer material doesn't show up viewer

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 7.38%. Comparing base (4a2233e) to head (07a909f).

Additional details and impacted files

@@          Coverage Diff          @@
##             dev    #252   +/-   ##
=====================================
  Coverage   7.38%   7.38%           
=====================================
  Files        243     243           
  Lines       4767    4767           
  Branches     564     564           
=====================================
  Hits         352     352           
  Misses      4400    4400           
  Partials      15      15           

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