dating extraction: failing to convert dating into span
somehow this case is not recognized correctly
{
"identifier": "6114227",
"onDating": [
"Original: hellenistisch <a href=\"http://chronontology.dainst.org/period/PKhlDWz28lrD\" target=\"_blank\">(Chronontology)</a> 3. Jh. v. Chr. (um oder bald nach 300 v. Chr.) / nach: H. J. Allendorf und A. Zimmermann"
],
"dating": [
[
"3. Jh. v. Chr.",
"300 v. Chr."
]
],
"datingSpan": [
[
null,
null
]
]
}```