Closable tabs not always displaying widgets

[c-dives]

ALL software version info

panel - 0.12.6
bokeh - 2.4.2
python - 3.9
firefox - 95.0.1
ubuntu - 20.04.3 LTS

Description of expected behavior and the observed behavior

Expected: Removing all tabs using the closable X and then adding a tab will display the contents of the new tab.

Observed: Removing all tabs using the closable X (Browser javascript console shows error after last tab is closed.) and then adding one or more tabs will display the tab title only, contents are not displayed until after clicking on the tab title.

Complete, minimal, self-contained example code that reproduces the issue

import panel as pn

add_button = pn.widgets.Button(name='Add Tab')
some_tabs = pn.Tabs(closable=True)

def add_button_callback(*_):
    some_tabs.append(pn.widgets.StaticText(name='Some Title', value="Some Text"))
add_button.on_click(add_button_callback)
col = pn.Column(add_button, some_tabs)
col.servable()

Stack traceback and/or browser JavaScript console output

Screenshots or screencasts of the bug in action

tabs_example.mp4