[glyf] Don't accept gids higher than maxp's glyphs number

This specially becomes concerning on sub-components where a gvar table
that is sanitized using maxp's glyphs number overflows when a high gid
accepted here goes to it, maybe an additional check can be put there
also, this however feels to be enough.

Fixes https://crbug.com/oss-fuzz/20944

src/hb-ot-glyf-table.hh

@@ -847,6 +847,7 @@ struct glyf
       glyf_table = hb_sanitize_context_t ().reference_table<glyf> (face);
 
       num_glyphs = hb_max (1u, loca_table.get_length () / (short_offset ? 2 : 4)) - 1;
+      num_glyphs = hb_min (num_glyphs, face->get_num_glyphs ());
     }
 
     void fini ()