[Linux][ProBuilder] - Crashes when selecting probuilder geometry.

Steps to Reproduce
- Open Unity 2018.1.0b12 with Ubuntu 16.04 LTS.
- Create a new project.
- Open Package manager.
- Select "All".
- Find and install Pro-builder.
- Select tools > Pro Builder > Pro-builder menu.
- Use Pro-builder to add a simple cube.
- Click generate (Cube might have overlapping UV's)
- Cube appears orange.
- Select cube
Notice issue >> Crash.