RadiationCT/Waterphantom testcases (esp. with Sn) break for higher moments

- Config files from KiTRTPaperData seem to work for 13 moments
- Config files with smaller mesh, density one but same number of moments also work
- when increasing moments to 20, solver breaks -> mass explodes, then becomes -nan, flux is inf then -nan
- Edit: the breaking point is 20 moments, below everything is fine, above problems ensue -> maybe the StarMap/physical data only goes up to 19?
