Guard against FPE in MaterialMapper, fix mapping scripts
Fix an FPE in MaterialMapper.cxx when we attempt to divide by 0. I'm not sure if this is expected and simply wasn't handled before, or if it's a bug in the geometry or step collection. Maybe @ncalace can advise.
I'm also removing attempting to store the configuration to pkl from some material mapping related scripts. This seems to error out after the main job completes with an error from inside the configuration code (sequence checking doesn't work). I don't believe we need this for the mapping process.