Indexing issues in Sgroups created as match to query molecule with unfolded hydrogens

[NadezhdaKatcman]

Summary
Sgroup created based on match have issues with atoms indexing, if it is created using query molecule with unfolded hydrogens

Steps to Reproduce

1. Have molecule uploaded or created using indigo (later called: Target molecule)
2. Have query molecule that is also a part of the target molecule
3. Unfold hydrogens in query molecule ("query.unfoldHydrogens()")
4. Use matcher to search query molecule in the target molecule
5. Create sgroup using found match
6. Iterate through sgroup's atoms trying to use their labels

Python script to reproduce the issue:
`indigo = Indigo()

mol = indigo.createMolecule()
mol.addAtom("C")

query = indigo.createQueryMolecule()
query.addAtom("C")

query.unfoldHydrogens()

matcher = indigo.substructureMatcher(mol)
match = matcher.match(query)

if match:
sgroup = mol.createSGroup("SUP", match, "TEST")

for atom in sgroup.iterateAtoms():
print(f"matched atom found {atom.symbol()}")`

Actual behavior
Match is found and sgroup is created but error is thrown during iterate through sgroup atoms:

print(f"matched atom found {atom.symbol()}")
File "...\Python313\site-packages\indigo\indigo\indigo_object.py", line 1057, in symbol
return IndigoLib.checkResultString(self._lib().indigoSymbol(self.id))
File "...\Python313\site-packages\indigo\indigo\indigo_lib.py", line 1178, in checkResultString
return IndigoLib.checkResultPtr(result, exception_class).decode()
File "...\Python313\site-packages\indigo\indigo\indigo_lib.py", line 1171, in checkResultPtr
raise exception_class(IndigoLib.lib.indigoGetLastError())
indigo.indigo.indigo_exception.IndigoException: array: invalid index -3 (size=1)

Expected behavior
There should be no error, all atoms from sgroup should be successfully processed and their labels printed

Environment details:

• indigo: 1.40.0
• python 3.13
• Windows 11 Enterprise. Version 25H2

Additional context

• This issue can be reproduced for other types of sgroups
• This issue can be reproduced also for target molecule with unfolded hydrogens
• There is no such issue if hydrogens are not unfolded in the query molecule
• Looks like this issue can have similar root with the issues:
  -- Two V3000 export issues: implict H cause wrong index on s groups, and reversed order for COLLECTON / SGroup Blocks. #2109
  -- After clicking the 'Save as...' button, an error message appears: (array: invalid index -2 (size=0)) #1318