BUG: Was trying to read an ods file and ran into UnboundLocalError in odfreader.py
- [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.

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

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

```python
for file in os.listdir('data'): pandas.read_excel(pathlib.Path('data', file), engine='odf')

```
Sorry I don't have a minimal data example at this time.

#### Problem description

Was trying to test pandas reading a collection of ods files and ran into this error.
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/util/_decorators.py", line 296, in wrapper
    return func(*args, **kwargs)
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_base.py", line 311, in read_excel
    return io.parse(
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_base.py", line 906, in parse
    return self._reader.parse(
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_base.py", line 443, in parse
    data = self.get_sheet_data(sheet, convert_float)
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_odfreader.py", line 91, in get_sheet_data
    value = self._get_cell_value(sheet_cell, convert_float)
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_odfreader.py", line 175, in _get_cell_value
    return self._get_cell_string_value(cell)
  File "/home/michael/.local/share/virtualenvs/merge-csv-NFbvYFrS/lib/python3.8/site-packages/pandas/io/excel/_odfreader.py", line 211, in _get_cell_string_value
    value.append(" " * spaces)
UnboundLocalError: local variable 'spaces' referenced before assignment
```

I took a look at the [code in question](https://github.com/pandas-dev/pandas/blob/ddf4f2430dd0a6fd51d7409ad3f524aeb5cbace2/pandas/io/excel/_odfreader.py#L211) and it seems like the line may be on the wrong indent level?

#### Expected Output

The usual dataframes :+1: 

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

<details>

INSTALLED VERSIONS
------------------
commit           : d9fff2792bf16178d4e450fe7384244e50635733
python           : 3.8.2.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.4.0-42-generic
Version          : #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.1.0
numpy            : 1.19.1
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 44.0.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : 1.0.1
pymysql          : None
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pyxlsb           : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : None

</details>
