unpack interactive dataframe `.shape` got KeyError

## Version

```
python: 3.11
jupyterlab: 4.0.3

pandas: 2.0.2
numpy: 1.24.3

hvplot: 0.8.4
```

## Problem

I was trying [this demo](https://panel.holoviz.org/gallery/portfolio_optimizer.html), found interactive dataframe went error in two places:

`np.nanmean` and `_, cols = dfi.shape`

## Code

I can reproduce the issue with the following code:

```python
import pandas as pd
import numpy as np
import hvplot.pandas

df = pd.DataFrame(np.random.randn(5, 5))
dfi = df.interactive()
```

### Problem 1

```python
np.nanmean(df, axis=0) # OK
# array([ 0.09263235, -0.61521997, 0.87237865, -0.65929222, -0.61866116])

np.nanmean(dfi, axis=0) # result is nan with warning: RuntimeWarning: Mean of empty slice
# nan
```

### Problem 2

```
rows, cols = dfi.shape
```

```
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
File D:\Code\.Envs\work\Lib\site-packages\pandas\core\indexes\base.py:3652, in Index.get_loc(self, key)
3651 try:
-> 3652 return self._engine.get_loc(casted_key)
3653 except KeyError as err:

File D:\Code\.Envs\work\Lib\site-packages\pandas\_libs\index.pyx:147, in pandas._libs.index.IndexEngine.get_loc()

File D:\Code\.Envs\work\Lib\site-packages\pandas\_libs\index.pyx:176, in pandas._libs.index.IndexEngine.get_loc()

File pandas\_libs\hashtable_class_helper.pxi:7080, in pandas._libs.hashtable.PyObjectHashTable.get_item()

File pandas\_libs\hashtable_class_helper.pxi:7088, in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 1

The above exception was the direct cause of the following exception:

KeyError Traceback (most recent call last)
Cell In[7], line 1
----> 1 rows, cols = dfi.shape

File D:\Code\.Envs\work\Lib\site-packages\hvplot\interactive.py:653, in Interactive.__getitem__(self, other)
651 def __getitem__(self, other):
652 other = other._transform if isinstance(other, Interactive) else other
--> 653 return self._apply_operator(operator.getitem, other)

File D:\Code\.Envs\work\Lib\site-packages\hvplot\interactive.py:539, in Interactive._apply_operator(self, operator, reverse, *args, **kwargs)
537 transform = new._transform
538 transform = type(transform)(transform, operator, *args, reverse=reverse)
--> 539 return new._clone(transform)

File D:\Code\.Envs\work\Lib\site-packages\hvplot\interactive.py:388, in Interactive._clone(self, transform, plot, loc, center, dmap, copy, max_rows, **kwargs)
386 else:
387 kwargs = dict(self._inherit_kwargs, **dict(self._kwargs, **kwargs))
--> 388 return type(self)(self._obj, fn=self._fn, transform=transform, plot=plot, depth=depth,
389 loc=loc, center=center, dmap=dmap, _shared_obj=self._shared_obj,
390 max_rows=max_rows, **kwargs)

File D:\Code\.Envs\work\Lib\site-packages\hvplot\interactive.py:282, in Interactive.__init__(self, obj, transform, fn, plot, depth, loc, center, dmap, inherit_kwargs, max_rows, method, _shared_obj, _current, **kwargs)
280 self._current_ = _current
281 else:
--> 282 self._current_ = self._transform.apply(ds, keep_index=True, compute=False)
283 self._init = True
284 self._dirty = False

File D:\Code\.Envs\work\Lib\site-packages\holoviews\util\transform.py:774, in dim.apply(self, dataset, flat, expanded, ranges, all_values, keep_index, compute, strict)
772 drange = ranges.get(eldim, {})
773 drange = drange.get('combined', drange)
--> 774 data = self._apply_fn(dataset, data, fn, fn_name, args,
775 kwargs, accessor, drange)
776 drop_index = keep_index_for_compute and not keep_index
777 compute = not compute_for_compute and compute

File D:\Code\.Envs\work\Lib\site-packages\holoviews\util\transform.py:674, in dim._apply_fn(self, dataset, data, fn, fn_name, args, kwargs, accessor, drange)
672 raise e
673 else:
--> 674 data = fn(*args, **kwargs)
676 return data

File D:\Code\.Envs\work\Lib\site-packages\pandas\core\frame.py:3761, in DataFrame.__getitem__(self, key)
3759 if self.columns.nlevels > 1:
3760 return self._getitem_multilevel(key)
-> 3761 indexer = self.columns.get_loc(key)
3762 if is_integer(indexer):
3763 indexer = [indexer]

File D:\Code\.Envs\work\Lib\site-packages\pandas\core\indexes\base.py:3654, in Index.get_loc(self, key)
3652 return self._engine.get_loc(casted_key)
3653 except KeyError as err:
-> 3654 raise KeyError(key) from err
3655 except TypeError:
3656 # If we have a listlike key, _check_indexing_error will raise
3657 # InvalidIndexError. Otherwise we fall through and re-raise
3658 # the TypeError.
3659 self._check_indexing_error(key)

KeyError: 1
```