chore: add name check for dataframes

Author: abelaba

src/optimagic/parameters/tree_registry.py

@@ -182,6 +182,7 @@ def _unflatten_df_optree(aux_data, leaves):
         sr.tolist(),
         {"index": sr.index, "name": sr.name},
         list(sr.index.map(_index_element_to_string)),
+        _get_names_pandas_dataframe(sr),
     ),
     lambda aux_data, leaves: pd.Series(leaves, **aux_data),
     namespace=extended_namespace,