Intempestive call with None args in DynamicMaps if hv.Dimension with unit is provided

[TheoMathurin]

The issue was introduced in the 1.3.0 release. It does come from Panel as I'm using the same HoloViews version (1.18.1) and it works fine with Panel 1.2.3.

Following #5535, I added units to kdims in my DynamicMaps.

This causes an issue where the callable is called twice on render, once with the expected kdim value and then once with None. Any subsequent slider manipulation does not trigger calls as presumably the value remains None.

Consider the following code, if you set the unit to None it works, but anything else leads to a second call with f=None.

import numpy as np
import holoviews as hv
import panel as pn

hv.extension('bokeh')


def function(f):
    print(f)
    if f is None:
        f = 0
    return hv.Curve((x, np.sin(f*x)))

x = np.linspace(0, 10)
unit = 'unit'
factor = hv.Dimension('factor', unit=unit)
dmap = hv.DynamicMap(function, kdims=factor).opts(width=600)
dmap = dmap.redim.values(factor=[1, 2, 3, 4, 5])

pn.Column(dmap).servable()

Note that this does not happen for HoloMaps.

No error is logged either in Python or in the browser.