Error when displaying the same chat.ChatFeed multiple times in Panel 1.6.1

[s-alexey]

Hi team, thanks for the amazing work you're doing!

I encountered an issue while trying to update to a newer version of Panel. I believe it was introduced by this commit as old_objects may be empty in

panel/panel/layout/feed.py

Line 162 in b245bbb

not any(isIn(old_objects[i], self.objects) for i in range(*self._last_synced))

ALL software version info

Software Version Info

Python==3.11 in [Colab](https://colab.research.google.com/drive/1MV4UtSYRGM4Dx5sGqtCoGVk7vKIMsRDL?usp=sharing), VScode and other Jupyter notebooks

panel==1.6.1
bokeh==3.6.3
jupyter_bokeh==4.0.5

Description of expected behavior and the observed behavior

The chat.ChatFeed should display correctly without errors, even when displayed multiple times.

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

import panel as pn 
from IPython import display

pn.extension()

feed = pn.chat.ChatFeed(objects=[pn.chat.ChatMessage("Hello")])

display.display(feed)
display.display(feed)

Stack traceback and/or browser JavaScript console output

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
[/usr/local/lib/python3.11/dist-packages/IPython/core/formatters.py](https://localhost:8080/#) in __call__(self, obj, include, exclude)
    968 
    969             if method is not None:
--> 970                 return method(include=include, exclude=exclude)
    971             return None
    972         else:

11 frames
[/usr/local/lib/python3.11/dist-packages/panel/layout/feed.py](https://localhost:8080/#) in <genexpr>(.0)
    160             self._last_synced and
    161             'visible_range' not in events and
--> 162             not any(isIn(old_objects[i], self.objects) for i in range(*self._last_synced))
    163         ):
    164             with edit_readonly(self):

IndexError: list index out of range
ChatFeed(_placeholder=ChatMessage, sizing_mode='stretch_width')
    [0] ChatMessage(object='Hello', user='User', reactions=[])

Screenshots or screencasts of the bug in action

Here is a notebook

• I may be interested in making a pull request to address this