Merged requested to merge kmorel/vtk-m:safer-divide-by-volume into master
While going through the VTK-m code to identify where a cast-and-call was
happening against VTKM_DEFAULT_TYPE_LIST, I ran into a subtle case in
ParticleDensityBase that was calling a worklet with an
UnknownArrayHandle. This works OK, but was probably compiling for
unnecessary types (for example, vectors). Changed the field resolution
to be more intentional.