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