fix(pandas): set `to_spec` dtype to None
`to_spec` returns `dtype` with `dtype.name` if dtype is not None.
@@ -788,7 +788,7 @@ class PandasSeries(
"id": self.descriptor_id,
"args": {
"orient": self._orient,
- "dtype": self._dtype.name,
+ "dtype": None if self._dtype is None else self._dtype.name,
"shape": self._shape,
"enforce_dtype": self._enforce_dtype,
"enforce_shape": self._enforce_shape,
