BUG: Fixed Series.align(frame) with ExtensionArray
Closes https://github.com/pandas-dev/pandas/issues/20576

cc @jorisvandenbossche 
That fixed it! Thanks # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20580?src=pr&el=h1) Report
> Merging [#20580](https://codecov.io/gh/pandas-dev/pandas/pull/20580?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4efb39f01f5880122fa38d91e12d217ef70fad9e?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/20580/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/20580?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #20580      +/-   ##
==========================================
+ Coverage   91.82%   91.82%   +<.01%     
==========================================
  Files         152      152              
  Lines       49255    49255              
==========================================
+ Hits        45226    45228       +2     
+ Misses       4029     4027       -2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.21% <100%> (ø)` | :arrow_up: |
| #single | `41.9% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/20580?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/20580/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `87.85% <100%> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/20580/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `84.73% <0%> (+0.2%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20580?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/20580?src=pr&el=footer). Last update [4efb39f...c26c454](https://codecov.io/gh/pandas-dev/pandas/pull/20580?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
