hvplot fails for DataFrame with index name of 0

#### ALL software version info
hvplot 0.8.1
#### Description of expected behavior and the observed behavior
a DataFrame has a index named 0 ( the int type). This is allowed i guess
#### Complete, minimal, self-contained example code that reproduces the issue

```
df2 = pd.DataFrame([1,2,3],pd.date_range(start='2000-01-01',periods=3, freq='6T'))
df2.index.name = 0
df2.hvplot() # fails
```

#### Stack traceback and/or browser JavaScript console output
```
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[49], line 7
3 df2.index.name = 0
5 df2
----> 7 df2.hvplot()

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/plotting/core.py:92, in hvPlotBase.__call__(self, x, y, kind, **kwds)
89 plot = self._get_converter(x, y, kind, **kwds)(kind, x, y)
90 return pn.panel(plot, **panel_dict)
---> 92 return self._get_converter(x, y, kind, **kwds)(kind, x, y)

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/converter.py:1240, in HoloViewsConverter.__call__(self, kind, x, y)
1238 dataset = Dataset(data)
1239 dataset = dataset.redim(**self._redim)
-> 1240 obj = method(x, y)
1241 obj._dataset = dataset
1243 if self.crs and self.project:
1244 # Apply projection before rasterizing

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/converter.py:1645, in HoloViewsConverter.line(self, x, y, data)
1643 def line(self, x=None, y=None, data=None):
1644 self._error_if_unavailable('line')
-> 1645 return self.chart(Curve, x, y, data)

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/converter.py:1609, in HoloViewsConverter.chart(self, element, x, y, data)
1607 def chart(self, element, x, y, data=None):
1608 "Helper method for simple x vs. y charts"
-> 1609 data, x, y = self._process_chart_args(data, x, y)
1610 if x and y and not isinstance(y, (list, tuple)):
1611 return self.single_chart(element, x, y, data)

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/converter.py:1576, in HoloViewsConverter._process_chart_args(self, data, x, y, single_y, categories)
1573 elif not self.gridded_data:
1574 data = self._transform_columnar_data(data)
-> 1576 x = self._process_chart_x(data, x, y, single_y, categories=categories)
1577 y = self._process_chart_y(data, x, y, single_y)
1579 # sort by date if enabled and x is a date

File ~/miniforge3/envs/schism_viz/lib/python3.8/site-packages/hvplot/converter.py:1553, in HoloViewsConverter._process_chart_x(self, data, x, y, single_y, categories)
1550 x = xs[0] if len(xs) else None
1552 if not x and not categories:
-> 1553 raise ValueError('Could not determine what to plot. Set x explicitly')
1554 return x

ValueError: Could not determine what to plot. Set x explicitly
```