Resampling with NaT in TimedeltaIndex raises MemoryError
- [x] closes #13223
- [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/22253?src=pr&el=h1) Report
> Merging [#22253](https://codecov.io/gh/pandas-dev/pandas/pull/22253?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3bcc2bb4e275efef6d4d4d87ac1d661aa4c2bdbc?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/22253/graphs/tree.svg?width=650&src=pr&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/22253?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #22253      +/-   ##
==========================================
- Coverage   92.07%   92.07%   -0.01%     
==========================================
  Files         169      169              
  Lines       50684    50682       -2     
==========================================
- Hits        46668    46666       -2     
  Misses       4016     4016
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.48% <100%> (-0.01%)` | :arrow_down: |
| #single | `42.34% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22253?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/22253/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `96.08% <100%> (-0.01%)` | :arrow_down: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/22253/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.25% <0%> (-0.09%)` | :arrow_down: |
| [pandas/util/\_depr\_module.py](https://codecov.io/gh/pandas-dev/pandas/pull/22253/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlcHJfbW9kdWxlLnB5) | `67.44% <0%> (+2.32%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22253?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/22253?src=pr&el=footer). Last update [3bcc2bb...1a7d3dc](https://codecov.io/gh/pandas-dev/pandas/pull/22253?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
