Steps to replicate:
1. Open the provided Unity project
2. From the Hierarchy open PBR Render Target
3. In the Inspector view, press Load Octane and then Render then View Source
4. In the bottom left window select Scene tab instead on Node graph
5. Select "Rearrange the items in this graph to make it look tidier" (second icon from the top) from the left side menu in the same window
6. Select Cubes Object layer map item in the Scene tab and right-click on it and press expand items
7. Repeat step 6 for the Plane object

Expected result: A crash does not occur
Actual result: Unity editor crashes

Reproducible with: 2017.1.0f3, 2017.3.0b1

Note: It is important that steps 6 and 7 would be done as fast as possible otherwise the crash does not occur every time