bug#66431: [PATCH] Fix reset treesit--explorer-last-node when explorer buffer was killed

[Eli Zaretskii]

> From: nvp <noah.v.peart@gmail.com>
> Date: Mon, 9 Oct 2023 23:02:48 -0700
> 
> Tags: patch
> 
> Bug: After `treesit-explorer-mode` is enabled in a buffer and its
> associated `treesit--explorer-buffer` is killed, a subsequent call
> to `treesit-explorer-mode` initially displays an empty explorer
> buffer b/c `treesit--explorer-refresh` sees old value for
> `treesit--explorer-last-node`.
> 
> * lisp/treesit.el (treesit-explorer-mode): reset
> `treesit--explorer-last-node` when `treesit--explorer-buffer` was killed
> 
> In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
> 3.24.33, cairo version 1.16.0) of 2023-10-05 built on noah-X580VD
> Repository revision: 505c80623049d9e181918acdac8229c9a2041b1e
> Repository branch: master
> Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
> System Description: Ubuntu 22.04.3 LTS

Yuan, could you please look into this?  Is the patch OK to go in, and
if so, should it be installed on emacs-29?