Speed up ring detection by reducing allocations (#5654)
Speed up ring detection by reducing allocations (#5654)

For an example large ring system, getSymmSSSR() took 3minutes.
After this trivial change, it went down to 2min 30s. I recognize
that's not much, but the change is _so_ minor I think that it's
still worth pushing.

Unfortunately, I can't share the structure :(
bp-kelley/rdkit,ptosco/rdkit,rdkit/rdkit,bp-kelley/rdkit,rdkit/rdkit,rdkit/rdkit,bp-kelley/rdkit,ptosco/rdkit,ptosco/rdkit,rdkit/rdkit,ptosco/rdkit,bp-kelley/rdkit,rdkit/rdkit,ptosco/rdkit,bp-kelley/rdkit,bp-kelley/rdkit,bp-kelley/rdkit,ptosco/rdkit,bp-kelley/rdkit,rdkit/rdkit,ptosco/rdkit,rdkit/rdkit,ptosco/rdkit,rdkit/rdkit