Fixed construction / factorization of empty PA and IA
Closes https://github.com/pandas-dev/pandas/issues/23933
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=h1) Report
> Merging [#24599](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/62506ca3c37b6b0d84833a8329e50c000316250e?src=pr&el=desc) will **decrease** coverage by `49.34%`.
> The diff coverage is `57.14%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24599/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24599       +/-   ##
===========================================
- Coverage   92.38%   43.04%   -49.35%     
===========================================
  Files         166      166               
  Lines       52478    52485        +7     
===========================================
- Hits        48483    22593    -25890     
- Misses       3995    29892    +25897
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `43.04% <57.14%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVydmFsLnB5) | `38.04% <0%> (-55.01%)` | :arrow_down: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `43.03% <80%> (-55.49%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.37%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-95.46%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.17%)` | :arrow_down: |
| ... and [126 more](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24599?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/24599?src=pr&el=footer). Last update [62506ca...572f1d0](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=h1) Report
> Merging [#24599](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/62506ca3c37b6b0d84833a8329e50c000316250e?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24599/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24599      +/-   ##
==========================================
- Coverage   92.38%   92.38%   -0.01%     
==========================================
  Files         166      166              
  Lines       52478    52485       +7     
==========================================
+ Hits        48483    48489       +6     
- Misses       3995     3996       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <100%> (ø)` | :arrow_up: |
| #single | `43.05% <57.14%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.53% <100%> (+0.01%)` | :arrow_up: |
| [pandas/core/arrays/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2ludGVydmFsLnB5) | `93.08% <100%> (+0.04%)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24599/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24599?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/24599?src=pr&el=footer). Last update [62506ca...572f1d0](https://codecov.io/gh/pandas-dev/pandas/pull/24599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!