bug#52709: 29.0.50; Font-lock trying to use keywords before setting them up

[Eli Zaretskii]

> From: martin rudalics <rudalics@gmx.at>
> Date: Tue, 21 Dec 2021 18:59:30 +0100
> 
> When trying to ediff a C file or find occurrences in it on master I
> frequently get this error.  A typical backtrace looks like
> 
> 
> Debugger entered--Lisp error: (error "Font-lock trying to use keywords before 
> setting them up")
>    signal(error ("Font-lock trying to use keywords before setting them up"))
>    error("Font-lock trying to use keywords before setting them up")
>    font-lock-compile-keywords(nil)
>    font-lock-fontify-keywords-region(1 112 nil)
>    font-lock-default-fontify-region(1523 1532 nil)
>    c-font-lock-fontify-region(1523 1532)
>    c-force-redisplay(1523 1532)
>    apply(c-force-redisplay (1523 1532))
>    timer-event-handler([t 25023 28385 699506 nil c-force-redisplay (1523 
> 1532) nil 18000 nil])

I think this is bug#52297, which is still unsolved.