BUG: Concat with inner join and empty DataFrame
State: closed

 - [x] closes #15328
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master | flake8 --diff``
 - [x] whatsnew entry


Labels:
name: Bug
name: Reshaping
description: Concat, Merge/Join, Stack/Unstack, Explode

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15397?src=pr&el=h1) Report
> Merging [#15397](https://codecov.io/gh/pandas-dev/pandas/pull/15397?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2?src=pr&el=desc) will **decrease** coverage by `-0.06%`.
> The diff coverage is `n/a`.


```diff
@@            Coverage Diff             @@
##           master   #15397      +/-   ##
==========================================
- Coverage   90.42%   90.36%   -0.06%     
==========================================
  Files         134      135       +1     
  Lines       49377    49438      +61     
==========================================
+ Hits        44650    44677      +27     
- Misses       4727     4761      +34
```


| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15397?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/tools/concat.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL3Rvb2xzL2NvbmNhdC5weQ==) | `97.62% <ø> (ø)` | :white_check_mark: |
| [pandas/io/s3.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2lvL3MzLnB5) | `0% <ø> (-85%)` | :x: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `81.97% <ø> (-1.41%)` | :x: |
| [pandas/io/common.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2lvL2NvbW1vbi5weQ==) | `70% <ø> (-0.87%)` | :x: |
| [pandas/io/html.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2lvL2h0bWwucHk=) | `84.48% <ø> (-0.67%)` | :x: |
| [pandas/core/groupby.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS5weQ==) | `94.89% <ø> (-0.24%)` | :x: |
| [pandas/io/excel.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2lvL2V4Y2VsLnB5) | `79.39% <ø> (-0.16%)` | :x: |
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.47% <ø> (-0.01%)` | :x: |
| [pandas/core/reshape.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS5weQ==) | `99.25% <ø> (-0.01%)` | :x: |
| [pandas/stats/moments.py](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?src=pr&el=tree#diff-cGFuZGFzL3N0YXRzL21vbWVudHMucHk=) | `71.19% <ø> (ø)` | :white_check_mark: |
| ... and [36 more](https://codecov.io/gh/pandas-dev/pandas/pull/15397/changes?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15397?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/15397?src=pr&el=footer). Last update [ff0deec...47c8735](https://codecov.io/gh/pandas-dev/pandas/compare/ff0deecbc8f8e9ae3d274e5e7cd7c0056de1a6c2...47c8735d9c46204a6f5d43704fe8424925d21557?el=footer&src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
thanks @abaldenko !