In the workbench, switch on volume rendering in properties view, then uncheck the useGPU checkbox => crash:
gdb> backtrack full
...
Core was generated by `./bin/MitkDiffusion --BlueBerry.Clean'.
Program terminated with signal SIGABRT, Aborted.
...
Error: no override found for 'vtkRayCastImageDisplayHelper'.
So I think we need to define a default case in the Module
and make sure exactly 1 checkbox is selected there (Does Qt have radiobuttons?) in the Plugin or GUI.