warning: no glyph for character ... in font ...

[Federico Bruni]

Can anybody explain what this warning is about?

Parsing...
Interpreting music...[8][16][24][32]
Preprocessing graphical objects...
warning: no glyph for character U+279B in font 
`/usr/share/fonts/urw-base35/C059-Roman.otf'

The character is the one defined in this snippet:
https://lsr.di.unimi.it/LSR/Snippet?id=879

I get these warnings only when building a score within a toolbox 
container; it doesn't happen in a regular terminal. It's annoying 
because it's printed several times. I'm trying to reduce "false" errors 
in order to easily spot the real issues.

I guess it's something related to Fontconfig settings in the container.

Thanks in advance
Federico