How to reproduce:

1. Start Workbench
2. Load image (e.g. Pic3D.nrrd)
3. open properties view
4. turn on volumerendering -> works, gpu-based
5. uncheck "gpu" property -> crash

Notes:

• enabling CPU raycast using the volumerendering plugin also crashes
• this was not tested on most recent master but some (unrelated) feature branch