BUG: ValueError in Py3 applying stats over column level with skipna=False (#19720)

- [x] closes #19720
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=h1) Report
> Merging [#22010](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/322dbf4f812f47d4eaee5d8afa10e17acf6dbc67?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `83.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22010/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #22010      +/-   ##
==========================================
- Coverage   91.99%   91.99%   -0.01%     
==========================================
  Files         167      167              
  Lines       50578    50583       +5     
==========================================
+ Hits        46530    46534       +4     
- Misses       4048     4049       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.39% <83.33%> (-0.01%)` | :arrow_down: |
| #single | `42.17% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/groupby/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/22010/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9vcHMucHk=) | `96.17% <83.33%> (-0.19%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=footer). Last update [322dbf4...3b7f44a](https://codecov.io/gh/pandas-dev/pandas/pull/22010?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you rebase closing as stale. ping if you want to continue.