- SCM glyph_name = ly_assoc_get (alt, alist, SCM_BOOL_F);
- Stencil acc (fm->find_by_name (ly_scm2string (glyph_name)));
+ SCM glyph_name_scm = ly_assoc_get (alt, alist, SCM_BOOL_F);
+ if (!scm_is_string (glyph_name_scm))
+ {
+ me->warning (_f ("No glyph found for alteration: %s",
+ ly_scm2rational (alt).to_string ().c_str ()));
+ continue;
+ }
+
+ string glyph_name = ly_scm2string (glyph_name_scm);
+
+ Stencil acc (fm->find_by_name (glyph_name));