BUG: sort_index throws IndexError for some permutations (#26053)
- [x] closes #26053 
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] tests added / passed
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@190a69e`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26054/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #26054   +/-   ##
=========================================
  Coverage          ?   40.74%           
=========================================
  Files             ?      175           
  Lines             ?    52487           
  Branches          ?        0           
=========================================
  Hits              ?    21388           
  Misses            ?    31099           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #single | `40.74% <0%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/26054/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `33.87% <0%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26054?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/26054?src=pr&el=footer). Last update [190a69e...2caee96](https://codecov.io/gh/pandas-dev/pandas/pull/26054?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/26054?src=pr&el=h1) Report
> Merging [#26054](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b62e9aeac6b646a7d4a1f63d88dd15e347ad3719?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/26054/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26054      +/-   ##
==========================================
- Coverage   91.98%   91.98%   -0.01%     
==========================================
  Files         175      175              
  Lines       52372    52375       +3     
==========================================
- Hits        48177    48176       -1     
- Misses       4195     4199       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.53% <100%> (ø)` | :arrow_up: |
| #single | `40.7% <0%> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/26054/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.62% <100%> (+0.01%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26054/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26054/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.9% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26054?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/26054?src=pr&el=footer). Last update [b62e9ae...5dec93f](https://codecov.io/gh/pandas-dev/pandas/pull/26054?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Hello @jayanthkaturi! 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:





There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-04-24 20:09:41 UTC this is same/duplicate as the original issue. I updated the PR, pls let me know if anything else is required. Thanks! also pls merge master thanks @jayanthkaturi 