BUG: value_counts Int64 zero-size array to reduction
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [x] (optional) I have confirmed this bug exists on the master branch of pandas.

---

```python
pd.Series([], dtype='int64').value_counts()  # Series([], dtype: int64)
pd.Series([], dtype='Int64').value_counts()  # ValueError: zero-size array to reduction ...
```

#### Problem description
Found this while using `Int64` types in dask. Error occurred in `_meta.value_counts()`

#### Expected Output
Error not to occur.

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.6.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.19.113-1-MANJARO
machine          : x86_64
processor        : 
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.0.3
numpy            : 1.18.2
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 46.1.3.post20200325
Cython           : None
pytest           : 5.4.1
hypothesis       : None
sphinx           : None
blosc            : 1.9.0
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.1
IPython          : 7.13.0
pandas_datareader: None
bs4              : 4.9.0
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.2.1
numexpr          : None
odfpy            : None
openpyxl         : 3.0.3
pandas_gbq       : None
pyarrow          : 0.16.0
pytables         : None
pytest           : 5.4.1
pyxlsb           : None
s3fs             : 0.4.2
scipy            : 1.4.1
sqlalchemy       : 1.3.15
tables           : None
tabulate         : None
xarray           : 0.15.1
xlrd             : 1.2.0
xlwt             : None
xlsxwriter       : None
numba            : 0.48.0

</details>
