Why are there "empty" glyphs with FontAwesome v4?

[gavinr-maps]

1. Download FontAwesome v4.7.0 WOFF file here: https://unpkg.com/[email protected]/fonts/fontawesome-webfont.woff
2. Upload that file to https://opentype.js.org/glyph-inspector.html
   • Expected: All the glyphs should have images
   • Actual: There are "empty" glyphs at the beginning and end:

Does anyone have any idea why these glyphs are empty/blank?

[Connum]

Are you sure that these are not just empty glyphs in the font file itself? Can you open it in another font tool and see if there are glyphs in these positions?

[gavinr-maps]

I suppose there are similar open spaces when I open it in FontForge,

So I take your point that it's probably a font issue and not an issue with OpenType.js. Thanks for the response!