BUG: Render empty DataFrame as empty HTML table w/o raising IndexError.
 - [X] closes #15953 
 - [X] 1 test added / passed
 - [X] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [ ] whatsnew entry

A one line change to add an ``if clabels`` guard to clabels enumeration.

Returns HTML string consisting of empty table.

Help requested with format and placement of whatsnew entry.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=h1) Report
> Merging [#16441](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/49ec31bbaeca81a6f58fc1be26fe80f3ac188cdd?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16441/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16441      +/-   ##
==========================================
+ Coverage   90.42%   90.42%   +<.01%     
==========================================
  Files         161      161              
  Lines       51023    51024       +1     
==========================================
+ Hits        46138    46139       +1     
  Misses       4885     4885
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.26% <100%> (ø)` | :arrow_up: |
| #single | `40.17% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/formats/style.py](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvc3R5bGUucHk=) | `95.92% <100%> (+0.01%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16441?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/16441?src=pr&el=footer). Last update [49ec31b...5c40256](https://codecov.io/gh/pandas-dev/pandas/pull/16441?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/16441?src=pr&el=h1) Report
> Merging [#16441](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6614e266bca32771c761e904367eff10dd4c8979?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16441/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16441      +/-   ##
==========================================
+ Coverage   90.42%   90.42%   +<.01%     
==========================================
  Files         161      161              
  Lines       51023    51024       +1     
==========================================
+ Hits        46138    46139       +1     
  Misses       4885     4885
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.26% <100%> (ø)` | :arrow_up: |
| #single | `40.17% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/formats/style.py](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvc3R5bGUucHk=) | `95.92% <100%> (+0.01%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16441?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/16441?src=pr&el=footer). Last update [6614e26...d9c354d](https://codecov.io/gh/pandas-dev/pandas/pull/16441?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @JimStearns206 whoops looks like there were some extra commits in there. Are you on gitter? I can walk you through rebasing if you want. Basic idea is to

```
git fetch upstream
git rebase upstream/master
# fix any conflicts that come up
git push -f origin GH15953
``` Thanks!