resampling_when breaks with dynspread

```python
import numpy as np
df = pd.DataFrame({
# random
"longitude": np.random.uniform(-180, 180, 1000),
"latitude": np.random.uniform(-90, 90, 1000),
})

df.hvplot.points(
"longitude",
"latitude",
rasterize=True,
tiles="CartoDark",
geo=True,
resample_when=300,
cmap="fire",
dynspread=True
)
```

`ValueError: spreading can only be applied to Image or RGB Elements. Received object of type `