fix #292

[skinnider]

Fix for issue #292, which occurs when tabulate_molecules and write_structural_prior_CV are run with different versions of rdkit.

[seungchan-an]

Confirmed that the filtering works as intended -- invalid SMILES only within the mass window are correctly identified and removed.
As an optional improvement, since this change serves as a safeguard against potential rdkit version inconsistencies, it may be helpful to log a warning only when invalid SMILES are actually removed (e.g., len(invalid_idx) > 0).

[skinnider]

Sounds reasonable. Can you implement that @seungchan-an?