bug#39977: 28.0.50; Unhelpful stack trace

[Eli Zaretskii]

> From: martin rudalics <rudalics@gmx.at>
> Cc: enometh@meer.net, 39977@debbugs.gnu.org
> Date: Sat, 14 Mar 2020 19:55:34 +0100
> 
> Maybe the following two changes would not harm:
> 
> (1) In fast_set_selected_frame check whether FRAME is live before doing
>      selected_frame = frame;
> 
> (2) In display_mode_lines check whether new_frame is live before doing
> 
>      selected_frame = new_frame;
> 
>      and maybe also for old_selected_frame before
> 
>      selected_frame = old_selected_frame;

And what do you suggest to do if the frame at RHS is not live?

> I have no idea whether these could help in any way but since we are in
> redisplay and the selected frame has become dead all of a sudden ...

Why do you think this is a problem for redisplay?