bug#36166: 27.0.50; Crash visiting HELLO when fringe-mode is disabled

[Robert Pluim]

>>>>> On Tue, 11 Jun 2019 18:26:31 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Cc: 36166@debbugs.gnu.org
    >> Date: Tue, 11 Jun 2019 17:17:40 +0200
    >> 
    Eli> I think the important part is the test of s->font_not_found_p.  Can
    Eli> you see whether it's zero in the crash case?
    >> 
    >> Yes, itʼs 0.

    Eli> Thanks.  So I think this:

    Eli>       if (EQ (font->driver->type, Qns))

    Eli> should be amended like this:

    Eli>       if (!s->font_not_found_p && EQ (font->driver->type, Qns))

Are you sure? if font_not_found_p == 0, then this condition will be
true, and font == NULL here, so we get a crash.

Robert