Failure in groupby-apply if aggregating timedelta and datetime columns
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd
fname = 'foo.csv'

sample_data = '''clientid,datetime
A,2017-02-01 00:00:00
B,2017-02-01 00:00:00
C,2017-02-01 00:00:00'''
open(fname, 'w').write(sample_data)

df = pd.read_csv(fname)
df['datetime'] = pd.to_datetime(df.datetime)
df['time_delta_zero'] = df.datetime - df.datetime
# Next line fails w error message below
print df.groupby('clientid').apply(
	lambda ddf: pd.Series(dict(
		clientid_age = ddf.time_delta_zero.min(),
		date = ddf.datetime.min()
		))
	)

```
#### Problem description

The current behavior is that the groupby-apply line fails, with the error message indicated below.



#### Expected Output

  clientid    date                                 clientid_age
0       A      2017-02-01 00:00:00      0 days
1        B      2017-02-01 00:00:00      0 days
2        C      2017-02-01 00:00:00      0 days

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

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.10.final.0
python-bits: 64
OS: Darwin
OS-release: 16.4.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.1
nose: 1.3.7
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.24.1
numpy: 1.11.3
scipy: 0.18.1
statsmodels: 0.6.1
xarray: None
IPython: 5.1.0
sphinx: 1.4.6
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.6.1
blosc: None
bottleneck: 1.1.0
tables: 3.2.3.1
numexpr: 2.6.1
matplotlib: 1.5.3
openpyxl: 2.3.2
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.3
lxml: 3.6.4
bs4: 4.5.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.13
pymysql: None
psycopg2: 2.6.2 (dt dec pq3 ext lo64)
jinja2: 2.8
boto: 2.42.0
pandas_datareader: None





Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/groupby.py", line 651, in apply
    return self._python_apply_general(f)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/groupby.py", line 660, in _python_apply_general
    not_indexed_same=mutated or self.mutated)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/groupby.py", line 3343, in _wrap_applied_output
    axis=self.axis).unstack()
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/series.py", line 2043, in unstack
    return unstack(self, level, fill_value)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/reshape.py", line 408, in unstack
    return unstacker.get_result()
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/reshape.py", line 169, in get_result
    return DataFrame(values, index=index, columns=columns)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/frame.py", line 255, in __init__
    copy=copy)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/frame.py", line 432, in _init_ndarray
    return create_block_manager_from_blocks([values], [columns, index])
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/internals.py", line 3993, in create_block_manager_from_blocks
    construction_error(tot_items, blocks[0].shape[1:], axes, e)
  File "/Users/fieldc/anaconda/lib/python2.7/site-packages/pandas/core/internals.py", line 3967, in construction_error
    if block_shape[0] == 0:
IndexError: tuple index out of range

</details>
