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

[Robert Pluim]

>>>>> On Tue, 11 Jun 2019 17:59:54 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Cc: 36166@debbugs.gnu.org
    >> Date: Tue, 11 Jun 2019 16:51:31 +0200
    >> 
    >> w32 and X both check s->cmp, at least (although even then they check
    >> slightly different conditions), and they also handle COMPOSITE_GLYPH
    >> differently.
    >> 
    >> Itʼs easy enough to chuck in a check for font being NULL, but that
    >> feels like the wrong solution (and I donʼt know this code at all).

    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.

Robert