Fix inconsistent results for empty datasets describe 
- [✔ ]  closes https://github.com/pandas-dev/pandas/issues/41575
- [ ✔]  tests added / passed
- [✔ ]  Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them



Hi @jreback This PR is about fixing https://github.com/pandas-dev/pandas/issues/41575. Thank this currently fails on master right? Hello @weikhor! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

* In the file [`pandas/core/groupby/generic.py`](https://github.com/pandas-dev/pandas/blob/69ea1cd23f457be4c9c3b013f3891b306d4c0607/pandas/core/groupby/generic.py):

> [Line 1864:36](https://github.com/pandas-dev/pandas/blob/69ea1cd23f457be4c9c3b013f3891b306d4c0607/pandas/core/groupby/generic.py#L1864): [W292](https://duckduckgo.com/?q=pep8%20W292) no newline at end of file

* In the file [`pandas/tests/groupby/test_function.py`](https://github.com/pandas-dev/pandas/blob/69ea1cd23f457be4c9c3b013f3891b306d4c0607/pandas/tests/groupby/test_function.py):

> [Line 1210:1](https://github.com/pandas-dev/pandas/blob/69ea1cd23f457be4c9c3b013f3891b306d4c0607/pandas/tests/groupby/test_function.py#L1210): [E302](https://duckduckgo.com/?q=pep8%20E302) expected 2 blank lines, found 1



##### Comment last updated at 2021-06-08 16:24:04 UTC > this currently fails on master right?
Yes
 This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. Thanks for the PR, but it appears that this has gone stale and needs to address the reviews. Closing due to inactivity but happy to reopen if you're interested in continuing.