bug#40418: 28.0.50; ERC quit server causes error in `erc-server-send-queue` timer

bug#40418: 28.0.50; ERC quit server causes error in `erc-server-send-queue` timer

[Narendra Joshi]

Using `erc-quit-server' command causes the following error:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (error "Selecting deleted buffer")
  erc-server-send-queue(#<killed buffer>)
  apply(erc-server-send-queue #<killed buffer>)
  timer-event-handler([t 24199 41423 723955 nil 
  erc-server-send-queue (#<killed buffer>) nil 886000])
--8<---------------cut here---------------end--------------->8---

The timer responsible for sending the message should have been 
cancelled before killing the buffer that is being passed to 
`erc-server-send-queue' function.  

In GNU Emacs 28.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version 
3.24.5, cairo version 1.16.0)
Repository revision: 1276c8e10b000b571a12227ebe9216cc6305ef7f
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 
11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

Best,
-- 
Narendra Joshi

bug#40418: 28.0.50; ERC quit server causes error in `erc-server-send-queue` timer

[Lars Ingebrigtsen]

Narendra Joshi <narendraj9@gmail.com> writes:

> Using `erc-quit-server' command causes the following error:
>
> Debugger entered--Lisp error: (error "Selecting deleted buffer")
>   erc-server-send-queue(#<killed buffer>)
>   apply(erc-server-send-queue #<killed buffer>)
>   timer-event-handler([t 24199 41423 723955 nil 
>   erc-server-send-queue (#<killed buffer>) nil 886000])
>
> The timer responsible for sending the message should have been 
> cancelled before killing the buffer that is being passed to 
> `erc-server-send-queue' function.  

If I'm reading the code correctly, the timer is only set in a variable
buffer-local to the killed buffer itself, so killing the timer isn't
trivial.  Instead I've made erc-server-send-queue check that the buffer
is live before trying to use it, which I think should fix this.

(Applied to Emacs 28.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no