added whatsnew entry

Author: SaturnFromTitan

doc/source/whatsnew/v1.0.0.rst

@@ -192,7 +192,8 @@ Other API changes
   Now, pandas custom formatters will only be applied to plots created by pandas, through :meth:`~DataFrame.plot`.
   Previously, pandas' formatters would be applied to all plots created *after* a :meth:`~DataFrame.plot`.
   See :ref:`units registration <whatsnew_1000.matplotlib_units>` for more.
--
+- An empty :class:`pandas.core.series.Series` now has the dtype ``object`` instead of ``float64``. The behaviour is now
+  consistent with the behaviour of :class:`pandas.core.frame.DataFrame` and :class:`pandas.core.indexes.base.Index`
 
 
 .. _whatsnew_1000.api.documentation: