Valence is lost for Mol and Rxn files

[Nitvex]

Steps to Reproduce

1. Convert the following ket-file to MolV3000:

{
    "root": {
        "nodes": [
            {
                "$ref": "mol0"
            }
        ]
    },
    "mol0": {
        "type": "molecule",
        "atoms": [
            {
                "label": "C",
                "location": [
                    12.678663862249214,
                    -6.7834675720035165,
                    0
                ],
                "charge": 2,
                "explicitValence": 1,
                "ringBondCount": -2,
                "substitutionCount": -1,
                "unsaturatedAtom": true,
                "invRet": 2
            }
        ]
    }
}

2. Get the result:

  -INDIGO-11162310432D

  0  0  0  0  0  0  0  0  0  0  0 V3000
M  V30 BEGIN CTAB
M  V30 COUNTS 1 0 0 0 0
M  V30 BEGIN ATOM
M  V30 1 C 12.6787 -6.78347 0.0 0 CHG=2 INVRET=2 UNSAT=1 SUBST=-1 RBCNT=-2
M  V30 END ATOM
M  V30 BEGIN BOND
M  V30 END BOND
M  V30 END CTAB
M  END

Expected behavior
Valence (VAL=1) is present in output molfile

Actual behavior
Valence is missing, despite being present in ket-file

Additional context
This behaviour also appears for .rxn files