If Series is called with no arguments, let it have a RangeIndex by default

Author: alanbato

pandas/core/series.py

@@ -173,6 +173,8 @@ def __init__(self, data=None, index=None, dtype=None, name=None,
 
             if data is None:
                 data = {}
+                if index is None:
+                    index = _default_index(0)
             if dtype is not None:
                 dtype = self._validate_dtype(dtype)