Merge pull request #5512 from RosettaCommons/vmullig/fix_randomize_bb_by_rama_prepro_if_no_selector_is_used
Minor fix for RandomizeBBByRamaPrePro mover.
This PR adds a little fix to RandomizeBBByRamaPrePro mover: previously, if a residue selector wasn't used, a cryptic error message would result. Now it should work.