bug#39133: 28.0.50; Emacs slowdown on special char

[Robert Pluim]

>>>>> On Fri, 24 Jan 2020 15:40:19 +0200, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Cc: lg.zevlg@gmail.com,  39133@debbugs.gnu.org,
    >> mituharu@math.s.chiba-u.ac.jp,  handa@gnu.org
    >> Date: Fri, 24 Jan 2020 14:09:22 +0100
    >> 
    >> >> Rather than duplicate that code, I moved the FONT_INVALID_CODE check
    >> >> up. This works for me:
    >> 
    Eli> Looks reasonable, thanks.
    >> 
    >> Except it crashes under -nw.

    Eli> Yes, because the call to the font driver should only be done when
    Eli> 'font_object' is a font object (it isn't on TTY frames).  Otherwise,
    Eli> simply assign FONT_INVALID_CODE to 'code'.

Yes, I worked that out. A simple crash, for once :-)

Robert