[BUG] Cannot clear active of RadiGroup

[maeglin89273]

Bug Description

Bokeh version 2.3.1
In the documentation, RadioGroup's active state is nullable. However, if I set active to None, the error occurs in the browser and the state remains. This still works in version 2.2.1.

Example Code

# test_radio_group.py
from bokeh.io import curdoc
from bokeh.models import Button, RadioGroup

clear_btn = Button(label='clear')
def clear_active():
    radio_btn_group.active = None

clear_btn.on_click(clear_active)
radio_btn_group = RadioGroup(labels=['a', 'b', 'c'], active=1)
curdoc().add_root(radio_btn_group)
curdoc().add_root(clear_btn)

run:
bokeh serve test_radio_group.py

Screenshots

Documentation

Browser Console Error

[bryevdv]

@maeglin89273 please add the missing portions of the example code so that it is a complete Minimal Reproducible Example

[maeglin89273]

@bryevdv Import statements added. Thanks!

[mattpap]

In bokeh RadioGroup.active can be nullable, but bokehjs doesn't allow this, both on API and implementation level. I have mixed feelings about allowing this.

[mattpap]

Actually given that RadioButtonGroup already supports this, then this should be considered as a bug.