BUG, dot product with empty dataframe
Dot product of empty dataframe resulted in dataframe filled with zeros. 
I thought the expected ones would be empty or NaN? 

In [3]: df = pd.DataFrame(index = ['a','b'])

In [4]: srs = pd.Series()

In [5]: df
Out[5]:
Empty DataFrame
Columns: []
Index: [a, b]

In [6]: srs
Out[6]: Series([], dtype: float64)

In [7]: df.dot(srs)
Out[7]:
a    0
b    0
dtype: float64
