Issue with deremining reaction family under the new functionality

[kfir4444]

Describe the bug
I am trying to determine the reaction family of a reaction:

[CH2] + C=C <=> C1CC1

Which is the most basic 1,2 cycloaddition. This fails for some reason.

How to reproduce

from arc.reaction import ARCReaction
from arc.species import ARCSpecies

rxn = ARCReaction(r_species = [ARCSpecies(label="r1", smiles="[CH2]"),
                               ARCSpecies(label="r2", smiles="C=C")],
                  p_species = [ARCSpecies(label="p1", smiles="C1CC1")])
rxn.determine_family() # (output: (None, None))
rxn.determine_family(rmg_family_set="all") # fails with KeyError: "RCH(OOH)CH2C(O)R'"

Expected behavior
Not to fail or crash

[alongd]

The issue here seems to be that the family requires CH2 to be a singlet, but the [CH2] SMILES are interpreted as a triplet. Anyway, I'll add this as a test to a future PR.

[alongd]

@kfir4444, this issue should be resolved by #852 now.
can you confirm?