Merge pull request #6570 from RosettaCommons/roccomoretti/fix_ThreadedRDKitRotamerLibrarySpecification_crash
[Foldit] Fix crash reported for some entries.
Crashes were reported which looked to trace to ThreadedRDKitRotamerLibrarySpecification and its embedding. Make that process more robust. (If we can't get a conformation for the ligands, just skip it.)
RELEASE NOTES: Fix crashes in ligand puzzles.