For information on mysterious FT_Get_Glyph_Name error message

[Peter Gentry]

I was baffled by the following messages. 

Preprocessing graphical objects...
programming error: FT_Get_Glyph_Name () error: invalid argument
continuing, cross fingers
programming error: Glyph has no name, but font supports glyph naming.
Skipping glyph U+10000080, file C:/Program 
Files/LilyPond/usr/share/lilypond/current/fonts/otf/CenturySchL-Roma.otf

After much commenting out I eventually discovered that one of my defined 
constants.

xdates = "(1833 - 1897)"  used in a markup as \xdates contained two non 
displaying characters (I've no idea what or how they got
there) and these caused the error message. 

The resultant pdf file was always as desired.

regards
Peter Gentry