sum of a column of an empty dataframe
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import pandas

# The following gives (0.0, False)
print(pandas.Series([]).sum(), pandas.DataFrame(columns=['col1'])['col1'].sum())

```
#### Problem description

In pandas 0.22, the sum of a column of an empty dataframe is False.  In earlier versions, 0.18.1 at least, the result would have been 0

While consistent with the default dtype of a DataFrame being obj, this isn't consistent with the 0.22 statement that the sum of an empty series is 0.0

#### Expected Output

(0.0, 0.0)

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.4.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-693.11.1.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.22.0
pytest: 3.3.0
pip: 9.0.1
setuptools: 36.5.0.post20170921
Cython: 0.27.3
numpy: 1.13.3
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.4
feather: None
matplotlib: 2.1.1
openpyxl: 2.4.9
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.1
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
